NE Noble Corporation PLC

As filed with the Securities and Exchange Commission on July 19, 2024

No. 333-280726

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

AMENDMENT NO. 1

TO

FORM S-4

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

Noble Corporation plc

(Exact name of registrant as specified in its charter)

13135 Dairy Ashford, Suite 800

Sugar Land, Texas 77478

(281) 276-6100

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Jennie P. Howard

Senior Vice President, General Counsel and Corporate Secretary

Noble Corporation plc

13135 Dairy Ashford, Suite 800

Sugar Land, Texas 7748

(281) 276-6100

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies of all communications, including communications sent to agent for service, should be sent to:

Approximate date of commencement of proposed sale to the public: As soon as practicable after this Registration Statement becomes effective and all other conditions to the proposed merger described in the enclosed proxy statement/prospectus have been satisfied or waived.

If the securities being registered on this Form are being offered in connection with the formation of a holding company and there is compliance with General Instruction G, check the following box. ☐

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act:

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act. ☐

If applicable, place an X in the box to designate the appropriate rule provision relied upon in conducting this transaction:

Exchange Act Rule 13e-4(i) (Cross-Border Issuer Tender Offer) ☐

Exchange Act Rule 14d-1(d) (Cross-Border Third-Party Tender Offer) ☐

The Registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the Registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933, as amended, or until the Registration Statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said Section 8(a), may determine.

The information in the accompanying proxy statement/prospectus is not complete and may be changed. We may not sell the securities offered by this proxy statement/prospectus until the registration statement filed with the Securities and Exchange Commission is effective. The accompanying proxy statement/prospectus does not constitute an offer to sell or a solicitation of an offer to buy any securities in any jurisdiction where an offer, solicitation or sale is not permitted.

PRELIMINARY, SUBJECT TO COMPLETION, DATED JULY 19, 2024

Diamond Offshore Drilling, Inc.

777 N. Eldridge Parkway, Suite 1100

Houston, Texas 77079

MERGER PROPOSED—YOUR VOTE IS VERY IMPORTANT

Dear Stockholders of Diamond Offshore Drilling, Inc.:

You are cordially invited to attend the special meeting of stockholders (the “special meeting”) of Diamond Offshore Drilling, Inc., a Delaware corporation (“Diamond Offshore”), to be held in the offices of Diamond Offshore located at 777 N. Eldridge Parkway, 12^th floor, Houston, Texas 77079, on [—], 2024, at [—] a.m., Central Time. Details regarding the meeting are provided in the accompanying Notice of Special Meeting of Stockholders and proxy statement/prospectus.

On June 9, 2024, Diamond Offshore entered into an Agreement and Plan of Merger (as it may be amended from time to time, the “merger agreement”) with Noble Corporation plc (“Noble”), Dolphin Merger Sub 1, Inc., an indirect wholly owned subsidiary of Noble (“Merger Sub 1”), and Dolphin Merger Sub 2, Inc., an indirect wholly owned subsidiary of Noble (“Merger Sub 2”), under which, and upon the terms and subject to the conditions set forth therein, Merger Sub 1 will be merged with and into Diamond Offshore (the “first merger”), with Diamond Offshore surviving and becoming an indirect wholly owned subsidiary of Noble, and immediately thereafter, Diamond Offshore, as the surviving entity in the first merger, will merge with and into Merger Sub 2 (the “second merger,” and together with the first merger, the “mergers”), with Merger Sub 2 surviving and continuing as an indirect wholly owned subsidiary of Noble.

At the effective time of the first merger (the “effective time”), each share of common stock, par value $0.0001 per share, of Diamond Offshore (“Diamond Offshore common stock”) issued and outstanding immediately prior to the effective time (other than any shares of Diamond Offshore common stock (i) owned by Diamond Offshore, Merger Sub 1, Merger Sub 2 or Noble or (ii) for which holders have demanded their rights to be paid the fair value of such share of Diamond Offshore common stock in accordance with Section 262 of the Delaware General Corporation Law), will be converted into the right to receive the following (collectively, the “merger consideration”): (a) $5.65 in cash, without interest, payable to the holder of each share of Diamond Offshore common stock; (b) 0.2316 of validly issued, fully paid and non-assessable A ordinary shares, $0.00001 nominal value per share, of Noble (“Noble ordinary shares”); and (c) any cash in lieu of fractional Noble ordinary shares to be paid pursuant to the merger agreement.

Subject to the terms of the merger agreement, at the effective time, each outstanding and unexercised warrant of Diamond Offshore (“Diamond Offshore warrants”) will be assumed by Noble and for 90 days after the effective time will remain outstanding and during such 90-day period will be exercisable for the merger consideration to which the holders would have been entitled upon consummation of the first merger, as if the holders of the Diamond Offshore warrants had exercised the warrants in full immediately prior to the effective time and acquired the applicable number of shares of Diamond Offshore common stock then issuable upon exercise of such warrants as a result of such exercise.

Subject to the terms of the merger agreement, at the effective time, each then outstanding performance-vesting restricted stock unit (a “PSU”) or time-vesting restricted stock unit (an “RSU”) covering shares of Diamond Offshore common stock (each, a “Diamond Offshore PSU” and a “Diamond Offshore RSU”, respectively) will cease to represent a right to receive shares of Diamond Offshore common stock (or value equivalent to shares of Diamond Offshore common stock) and will be converted into the right to acquire a number of Noble ordinary shares equal to the product of (i) the number of shares of Diamond Offshore common

stock subject to such Diamond Offshore PSU or Diamond Offshore RSU, as applicable, immediately prior to the effective time and (ii) the sum of (a) the exchange ratio plus (b) the quotient of (1) the per share cash consideration, divided by (2) the closing price on the New York Stock Exchange (the “NYSE”) for a Noble ordinary share on the last trading day immediately preceding the effective time of the second merger. Under this formula, Diamond Offshore PSUs will be converted into RSUs covering Noble ordinary shares (“Noble RSUs”) based on the greater of (x) actual Diamond Offshore performance level achieved and (y) target Diamond Offshore performance level, in each case, as determined under the performance criteria applicable to such Diamond Offshore PSUs, which Noble RSUs will otherwise vest on the same terms and conditions as were applicable under the Diamond Offshore PSUs, subject to certain adjustments for Diamond Offshore PSUs granted after the date of the merger agreement. Notwithstanding the foregoing, to the extent that a Diamond Offshore PSU or a Diamond Offshore RSU vests as of the effective time (including any awards that vest as a result of a termination of employment at or immediately after the effective time of the second merger), such awards will instead be settled in cash or shares of Diamond Offshore common stock, as applicable, immediately prior to the effective time and any such shares of Diamond Offshore common stock will be treated the same as other shares of Diamond Offshore common stock, as explained above.

Based on the closing price of Noble ordinary shares on June 7, 2024, the last full trading day before the public announcement of the execution of the merger agreement, the implied merger consideration to be received by Diamond Offshore stockholders is $15.52 per share of Diamond Offshore common stock. Based on the closing price of Noble ordinary shares on July 17, 2024, the last practicable date before the date of the accompanying proxy statement/prospectus, the implied merger consideration to be received by Diamond Offshore stockholders is $16.70 per share of Diamond Offshore common stock. The value of the merger consideration to be received in exchange for each share of Diamond Offshore common stock will fluctuate with the market value of the Noble ordinary shares until the effective time. The shares of Diamond Offshore common stock are listed on the NYSE under the symbol “DO.” Noble ordinary shares are listed and trade on the NYSE and the Nasdaq Copenhagen under the ticker symbols “NE” and “NOBLE,” respectively. We urge you to obtain current market quotations for shares of Diamond Offshore common stock and Noble ordinary shares.

Based upon the number of shares of Diamond Offshore common stock, the number of Diamond Offshore equity awards and the number of Noble ordinary shares, in each case, outstanding on July 17, 2024, the last practicable date before the date of the accompanying proxy statement/prospectus, we expect that, immediately after the consummation of the first merger, the former holders of Diamond Offshore common stock and Diamond Offshore equity awards immediately prior to the consummation of the first merger would own approximately 15%, and the holders of Noble ordinary shares immediately prior to the consummation of the first merger would own approximately 85%, of the outstanding fully diluted Noble ordinary shares. The number of Noble ordinary shares that will be issued in the first merger will depend on, among other factors, the number of shares of Diamond Offshore common stock and Diamond Offshore equity awards outstanding immediately prior to the effective time.

The first merger cannot be completed unless the affirmative vote of holders of a majority of the outstanding shares of Diamond Offshore common stock entitled to vote at the special meeting vote to adopt the merger agreement. Because of this, Diamond Offshore is holding the special meeting to vote on the proposal necessary to complete the first merger. Information about the meeting, the merger agreement, the transactions contemplated by the merger agreement (together with the mergers, the “transactions”) and the other business to be considered by Diamond Offshore stockholders at the special meeting is contained in the accompanying proxy statement/prospectus. The board of directors of Diamond Offshore (the “Diamond Offshore Board”) has fixed the close of business on July 19, 2024, as the record date for the determination of Diamond Offshore stockholders entitled to notice of, and to vote at, the special meeting. Any stockholder entitled to attend and vote at the special meeting is entitled to appoint a proxy to attend and vote on such stockholder’s behalf. Such proxy need not be a holder of shares of Diamond Offshore common stock. We urge you to read the accompanying proxy statement/prospectus and the annexes and documents incorporated into it by reference carefully. You should also carefully consider the risks that are described in the “Risk Factors” section beginning on page 27.

The Diamond Offshore Board has unanimously (i) determined that the merger agreement and the transactions, including the mergers, are fair to, and in the best interests of, Diamond Offshore and the holders of Diamond Offshore common stock, (ii) approved and declared advisable the merger agreement and the transactions, including the mergers, and (iii) resolved to recommend that the Diamond Offshore stockholders adopt and approve the merger agreement and the transactions, including the mergers.

The Diamond Offshore Board unanimously recommends that Diamond Offshore stockholders vote “FOR” the proposal to approve and adopt the merger agreement, “FOR” the advisory, non-binding proposal to approve the compensation that may be paid or become payable to Diamond Offshore’s named executive officers that is based on or otherwise related to the transactions and “FOR” the adjournment of the special meeting to solicit additional proxies if there are not sufficient votes to adopt the merger agreement.

Your vote is very important, regardless of the number of shares of Diamond Offshore common stock that you own. Whether or not you plan to attend the special meeting, please complete, sign and date the enclosed proxy and return it promptly in the enclosed postage-paid return envelope or give your proxy by telephone or over the Internet by following the instructions on the enclosed proxy card. You may revoke your proxy at any time prior to its exercise at the Diamond Offshore special meeting in the manner described in the proxy statement/prospectus accompanying this letter. Completing a proxy now will not prevent you from being able to vote at the special meeting by attending the special meeting and casting a vote. Your vote at the special meeting will supersede any previously submitted proxy.

If your shares are held in “street name,” you should instruct your broker, bank or other nominee how to vote your shares of Diamond Offshore common stock on each proposal in accordance with your voting instruction form.

Abstentions, broker non-votes and a failure to submit a proxy or attend and vote at the special meeting will have the same effect as a vote “AGAINST” the merger agreement.

Thank you for your continued support, interest and investment in Diamond Offshore.

Sincerely,

Bernie G. Wolford, Jr.

President and Chief Executive Officer

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the first merger or the other transactions described in the accompanying proxy statement/prospectus or the securities to be issued in connection with the first merger or determined if the accompanying proxy statement/prospectus is accurate or complete. Any representation to the contrary is a criminal offense.

The accompanying proxy statement/prospectus is dated [—], 2024, and is first being mailed to Diamond Offshore stockholders on or about [—], 2024.

Diamond Offshore Drilling, Inc.

777 N. Eldridge Parkway, Suite 1100

Houston, Texas 77079

NOTICE OF SPECIAL MEETING OF STOCKHOLDERS

To be held on [—], 2024

To the Stockholders of Diamond Offshore Drilling, Inc.:

We are pleased to invite you to attend the special meeting of stockholders (the “special meeting”) of Diamond Offshore Drilling, Inc., a Delaware corporation (“Diamond Offshore”), which will be held in the offices of Diamond Offshore located at 777 N. Eldridge Parkway, 12^th floor, Houston, Texas 77079, on [—], 2024, at [—] a.m., Central Time, for the following purposes as more fully described in the accompanying proxy statement/prospectus:

Diamond Offshore will transact no other business at the special meeting except such business as may properly be brought before the special meeting or any adjournment or postponement thereof by or at the direction of the board of directors of Diamond Offshore (the “Diamond Offshore Board”). Please refer to the proxy statement/prospectus of which this notice is a part for further information with respect to the business to be transacted at the special meeting.

Diamond Offshore fixed the close of business on July 19, 2024 as the record date for the special meeting (the “record date”). Only Diamond Offshore stockholders of record at the record date are entitled to receive notice of, and to vote at, the special meeting or any adjournment or postponement thereof. A complete list of Diamond Offshore stockholders entitled to vote at the special meeting will be available for inspection at 777 N. Eldridge Parkway, Suite 1100, Houston, Texas 77079 during regular business hours for a period of at least 10 days prior to the special

meeting. If you would like to inspect the list of Diamond Offshore stockholders of record, please call the Diamond Offshore Investor Relations department at (281) 492-5300 to schedule an appointment or request access. A certified list of eligible Diamond Offshore stockholders will be available for inspection during the special meeting.

Completion of the first merger is conditioned on adoption of the merger agreement by the Diamond Offshore stockholders, which requires the affirmative vote of holders of a majority of the outstanding shares of Diamond Offshore common stock entitled to vote thereon.

The Diamond Offshore Board has unanimously (i) determined that the merger agreement and the transactions, including the mergers, are fair to, and in the best interests of, Diamond Offshore and the holders of shares of Diamond Offshore common stock, (ii) approved and declared advisable the merger agreement and the transactions, including the mergers, and (iii) resolved to recommend that the Diamond Offshore stockholders adopt and approve the merger agreement and the transactions, including the mergers. The Diamond Offshore Board unanimously recommends that Diamond Offshore stockholders vote “FOR” the merger agreement proposal, “FOR” the advisory compensation proposal and “FOR” the adjournment proposal.

Your vote is very important regardless of the number of shares of Diamond Offshore common stock that you own. If you plan to attend the special meeting, please follow the instructions as outlined in the accompanying proxy statement/prospectus. Whether or not you expect to attend the special meeting, we urge you to submit your vote in advance of the special meeting. If your shares are held in the name of a broker, bank or other nominee, please vote by following the instructions on the enclosed voting instruction form furnished by the broker, bank or other nominee. If you hold your shares in your own name, submit a proxy to vote your shares as promptly as possible by (i) visiting the internet site listed on the accompanying proxy card, (ii) calling the toll-free number listed on the proxy card or (iii) marking, signing, dating and submitting your proxy card by mail by using the self-addressed, stamped envelope provided. Submitting a proxy will not prevent you from voting at the special meeting, but it will help to secure a quorum and avoid added solicitation costs if you decide not to or become unable to attend the special meeting. Any eligible holder of Diamond Offshore common stock may vote at the special meeting, thereby revoking any previous proxy. In addition, a proxy may also be revoked in writing before it is exercised at the special meeting in the manner described in the proxy statement/prospectus of which this notice is a part.

The proxy statement/prospectus of which this notice is a part provides a detailed description of the merger agreement, the transactions and the other matters to be considered at the special meeting. We urge you to carefully read the accompanying proxy statement/prospectus (including the annexes hereto) and any documents incorporated by reference herein in their entirety. In particular, we urge you to carefully read the section entitled “Risk Factors” beginning on page 27.

If you have any questions concerning the transactions or the accompanying proxy statement/prospectus, would like additional copies or need help voting your shares of Diamond Offshore common stock, please contact Diamond Offshore’s proxy solicitor:

Innisfree M&A Incorporated

501 Madison Avenue, 20th Floor

New York, NY 10022

Diamond Offshore stockholders may call: (877) 750-9497 (TOLL-FREE from the United States and Canada)

or +1 (412) 232-3651 (from other locations)

Banks and brokers may call collect: (212) 750-5833

REFERENCES TO ADDITIONAL INFORMATION

This proxy statement/prospectus incorporates by reference important business and financial information about Noble and Diamond Offshore from other documents that are not included in or delivered with this proxy statement/prospectus. For a listing of the documents incorporated by reference into this proxy statement/prospectus, see the section titled “Where You Can Find More Information” beginning on page 205.

You can obtain any of the documents incorporated by reference into this proxy statement/prospectus without charge by requesting them in writing or by telephone as follows:

For information related to Noble:

Noble Corporation plc

13135 Dairy Ashford, Suite 800

Sugar Land, Texas 77478

Attention: Investor Relations

Telephone: (281) 276-6100

For information related to Diamond Offshore:

Diamond Offshore Drilling, Inc.

777 N. Eldridge Parkway, Suite 1100

Houston, Texas 77079

Attention: Investor Relations

Telephone: (281) 647-4035

To receive timely delivery of the documents in advance of the special meeting of Diamond Offshore stockholders, you should make your request no later than [—], 2024, which is five business days before the special meeting.

You may also obtain any of the documents incorporated by reference into this proxy statement/prospectus without charge through the Securities and Exchange Commission (the “SEC”) website at www.sec.gov. In addition, you may obtain copies of documents filed by Noble with the SEC by accessing Noble’s website at www.noblecorp.com under the tab “Investors” and then under the heading “Reports & Filings.” You may also obtain copies of documents filed by Diamond Offshore with the SEC by accessing Diamond Offshore’s website at www.investor.diamondoffshore.com under the tab “Investor Relations.”

We are not incorporating the contents of the websites of the SEC, Noble, Diamond Offshore or any other entity into this proxy statement/prospectus. We are providing the information about how you can obtain certain documents that are incorporated by reference into this proxy statement/prospectus at these websites only for your convenience.

ABOUT THIS PROXY STATEMENT/PROSPECTUS

This proxy statement/prospectus, which forms part of a registration statement on Form S-4 filed with the SEC by Noble (File No. 333-280726), constitutes a prospectus of Noble under Section 5 of the Securities Act of 1933, as amended (the “Securities Act”), with respect to the A ordinary shares, $0.00001 nominal value per share, of Noble (“Noble ordinary shares”) to be issued to Diamond Offshore stockholders pursuant to the merger agreement. This document also constitutes a proxy statement of Diamond Offshore under Section 14(a) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). It also constitutes a notice of meeting with respect to the special meeting, at which Diamond Offshore stockholders will be asked to consider and vote on the adoption of the merger agreement and other related proposals.

Noble has supplied all information contained in this proxy statement/prospectus or incorporated by reference herein, relating to Noble, Merger Sub 1 and Merger Sub 2, and Diamond Offshore has supplied all such information relating to Diamond Offshore contained in this proxy statement/prospectus or incorporated by reference herein. Noble and Diamond Offshore have both contributed to the information relating to the merger agreement contained in this proxy statement/prospectus.

You should rely only on the information contained in this proxy statement/prospectus and the information incorporated by reference into this proxy statement/prospectus. Noble and Diamond Offshore have not authorized anyone to provide you with information other than the information that is contained in, or incorporated by reference into, this proxy statement/prospectus. Noble and Diamond Offshore take no responsibility for, and can provide no assurances as to the reliability of, any other information that others may give you. This proxy statement/prospectus is dated [—], 2024, and you should not assume that the information contained in this proxy statement/prospectus is accurate as of any date other than such date. Further, you should not assume that the information incorporated by reference into this proxy statement/prospectus is accurate as of any date other than the date of such document. Neither Noble nor Diamond Offshore assumes any obligation to update the information contained in this document (whether as a result of new information, future events or otherwise), except as required by applicable law. Neither the mailing of this proxy statement/prospectus to Diamond Offshore stockholders nor the issuance by Noble of the Noble ordinary shares pursuant to the merger agreement will create any implication to the contrary.

TABLE OF CONTENTS

i

ii

QUESTIONS AND ANSWERS ABOUT THE TRANSACTIONS AND THE SPECIAL MEETING

The following questions and answers briefly address some commonly asked questions about the transactions and the special meeting. They may not include all of the information that is important to Diamond Offshore stockholders. Diamond Offshore stockholders should carefully read this entire proxy statement/prospectus (including the annexes hereto) and the other documents referred to or incorporated by reference into this proxy statement/prospectus. See the section titled “Where You Can Find More Information” beginning on page 205 of this proxy statement/prospectus.

Q: What are the mergers and what effect will they have on Diamond Offshore?

Diamond Offshore Drilling, Inc. (“Diamond Offshore”) entered into an Agreement and Plan of Merger, dated June 9, 2024 (as it may be amended from time to time, the “merger agreement”), with Noble Corporation plc (“Noble”), Dolphin Merger Sub 1, Inc., an indirect wholly owned subsidiary of Noble (“Merger Sub 1”), and Dolphin Merger Sub 2, Inc., an indirect wholly owned subsidiary of Noble (“Merger Sub 2”). A copy of the merger agreement is attached as Annex A to this proxy statement/prospectus. The merger agreement contains the terms and conditions of the proposed acquisition of Diamond Offshore by Noble. Under the merger agreement, subject to satisfaction (or, to the extent permitted by law and in accordance with the merger agreement, waiver) of the conditions to the transactions set forth in the merger agreement and described in this proxy statement/prospectus, Merger Sub 1 will be merged with and into Diamond Offshore (the “first merger”), with Diamond Offshore surviving and becoming an indirect wholly owned subsidiary of Noble, and immediately thereafter, Diamond Offshore, as the surviving entity in the first merger, will merge with and into Merger Sub 2 (the “second merger,” and together with the first merger, the “mergers”), with Merger Sub 2 surviving and continuing as an indirect wholly owned subsidiary of Noble.

Following completion of the transactions contemplated by the merger agreement (together with the mergers, the “transactions”), Noble and Diamond Offshore will cooperate in taking or causing to be taken all actions necessary, proper or advisable to enable the delisting by Merger Sub 2, as the surviving entity in the second merger, of the shares of common stock, par value $0.0001 per share, of Diamond Offshore (the “Diamond Offshore common stock”) from the New York Stock Exchange (“NYSE”) and deregistering the shares of Diamond Offshore common stock under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), after which Merger Sub 2, as the surviving entity in the second merger, will no longer be required under the Securities and Exchange Commission’s (the “SEC”) rules and regulations to file periodic reports with the SEC in respect of the shares of Diamond Offshore common stock.

Q: Why am I receiving these materials?

Noble and Diamond Offshore are sending these materials to Diamond Offshore stockholders to help them decide how to vote their shares of Diamond Offshore common stock with respect to the first merger and other matters to be considered at the special meeting of Diamond Offshore stockholders (the “special meeting”) to be held in the offices of Diamond Offshore located at 777 N. Eldridge Parkway, 12^th floor, Houston, Texas 77079, on [—], 2024, at [—] a.m., Central Time.

Diamond Offshore is holding the special meeting to vote on the proposal to adopt the merger agreement and other related proposals. Information about the special meeting, the transactions and the other business to be considered by Diamond Offshore stockholders at the special meeting is contained in this proxy statement/prospectus. The first merger cannot be completed unless Diamond Offshore stockholders adopt the merger agreement with the affirmative vote of the holders of a majority of the outstanding shares of Diamond Offshore common stock entitled to vote thereon.

This proxy statement/prospectus constitutes both a prospectus of Noble and a proxy statement of Diamond Offshore. It is a prospectus because Noble will issue its ordinary shares in exchange for outstanding shares of Diamond Offshore common stock in the first merger. It is a proxy statement because the board of directors of Diamond Offshore (the “Diamond Offshore Board”) is soliciting proxies from Diamond Offshore stockholders.

1

Q: What will Diamond Offshore stockholders receive in the first merger?

At the effective time of the first merger (the “effective time”), each share of Diamond Offshore common stock issued and outstanding immediately prior to the effective time (other than any shares of Diamond Offshore common stock (i) owned by Diamond Offshore, Merger Sub 1, Merger Sub 2 or Noble or (ii) for which holders have demanded their rights to be paid the fair value of such share of Diamond Offshore common stock in accordance with Section 262 of the Delaware General Corporation Law (the “DGCL”)), will be converted into the right to receive the following (collectively, the “merger consideration”): (i) $5.65 in cash, without interest, payable to the holder of each share of Diamond Offshore common stock (the “per share cash consideration”); (ii) 0.2316 (the “exchange ratio”) of validly issued, fully paid and non-assessable A ordinary shares, $0.00001 nominal value per share, of Noble (“Noble ordinary shares”); and (iii) any cash in lieu of fractional Noble ordinary shares to be paid pursuant to the merger agreement.

The exchange ratio is fixed and will not be adjusted to reflect changes in the stock price of either Noble or Diamond Offshore between the date of the merger agreement and the effective time. The exchange ratio will, however, be adjusted in accordance with the terms of the merger agreement to fully reflect the effect of any stock dividend, stock split, stock combination or reclassification, with respect to outstanding shares of capital stock of either Noble or Diamond Offshore with a record date (as defined below) between the date of the merger agreement and the effective time.

No fractional Noble ordinary shares will be issued in connection with the first merger. Each Diamond Offshore stockholder that otherwise would have been entitled to receive a fractional Noble ordinary share will have the right to receive an amount in cash, without interest, rounded to the nearest cent, equal to the product of (i) the fractional share interest to which such holder (after taking into account all shares of Diamond Offshore common stock held at the effective time) would otherwise be entitled, by (ii) the closing price on the NYSE for a Noble ordinary share on the last trading day immediately preceding the effective time. For more details on the merger consideration, see the section titled “The Merger Agreement—Merger Consideration” beginning on page 122.

Q: What will the holders of outstanding Diamond Offshore equity awards receive in the first merger?

At the effective time, each then outstanding performance-vesting restricted stock unit (a “PSU”) or time-vesting restricted stock unit (an “RSU”) covering shares of Diamond Offshore common stock (each, a “Diamond Offshore PSU” and a “Diamond Offshore RSU,” respectively) will cease to represent a right to receive shares of Diamond Offshore common stock and will be converted, at the effective time, into the right to acquire a number of Noble ordinary shares equal to the product of (i) the number of shares of Diamond Offshore common stock subject to such Diamond Offshore PSU or Diamond Offshore RSU, as applicable, immediately prior to the effective time and (ii) the sum of (a) the exchange ratio plus (b) the quotient of (1) the per share cash consideration, divided by (2) the closing price on the NYSE for a Noble ordinary share on the last trading day immediately preceding the effective time of the second merger (the product of (i) and (ii), the “equity award consideration”). Under this formula, Diamond Offshore PSUs will be converted into RSUs covering Noble ordinary shares (“Noble RSUs”) based on the greater of (x) actual Diamond Offshore performance level achieved and (y) target Diamond Offshore performance level, in each case, as determined under the performance criteria applicable to such Diamond Offshore PSUs, which Noble RSUs will otherwise vest on the same terms and conditions as were applicable under the Diamond Offshore PSUs, subject to certain adjustments for Diamond Offshore PSUs granted after the date of the merger agreement. Notwithstanding the foregoing, to the extent that a Diamond Offshore PSU or a Diamond Offshore RSU vests as of the effective time (including any awards that vest as a result of a termination of employment at or immediately after the effective time of the second merger), such awards will instead be settled in cash or shares of Diamond Offshore common stock, as applicable, immediately prior to the effective time and any such shares of Diamond Offshore common stock will be treated the same as other shares of Diamond Offshore common stock, as explained above.

For additional information on certain other compensation-related matters covered in the merger agreement that affect Diamond Offshore’s directors and executive officers, please see the section titled “The Transactions—Interests of Directors and Executive Officers of Diamond Offshore in the Transactions” beginning on page 97.

2

Q: How are Diamond Offshore warrants treated in connection with the transactions?

Subject to the terms of the merger agreement, at the effective time, each outstanding and unexercised warrant of Diamond Offshore (“Diamond Offshore warrants”) will be assumed by Noble and for 90 days after the effective time will remain outstanding and during such 90-day period will be exercisable for the merger consideration to which the holders would have been entitled upon consummation of the first merger, as if the holders of the Diamond Offshore warrants had exercised the warrants in full immediately prior to the effective time and acquired the applicable number of shares of Diamond Offshore common stock then issuable upon exercise of such warrants as a result of such exercise.

Q: What equity stake will Diamond Offshore stockholders hold in Noble immediately following the completion of the first merger?

Upon the completion of the first merger, based on the exchange ratio, the estimated number of Noble ordinary shares issuable as the merger consideration is approximately 26.4 million shares, which will result in former holders of Diamond Offshore common stock and Diamond Offshore equity awards immediately prior to the consummation of the first merger holding approximately 15% of the outstanding fully diluted Noble ordinary shares following the completion of the first merger based on the number of outstanding Noble ordinary shares, shares of Diamond Offshore common stock and outstanding equity awards of Noble and Diamond Offshore as of July 17, 2024, the last practicable date before the date of this proxy statement/prospectus for which such information was available.

For more details on the merger consideration and the treatment of Diamond Offshore equity awards, see the section titled “The Merger Agreement—Merger Consideration” beginning on page 122 and “The Merger Agreement—Merger Consideration—Treatment of Diamond Offshore Equity Awards” beginning on page 125.

Q: When do Noble and Diamond Offshore expect to complete the transactions?

Noble and Diamond Offshore currently expect that the transactions will be completed by the first quarter of 2025. Neither Noble nor Diamond Offshore can predict, however, the actual date on which the transactions will be completed because they are subject to conditions beyond each of Noble’s and Diamond Offshore’s control. See the section titled “The Merger Agreement—Conditions to Completion of the Transactions” beginning on page 145.

Q: Is Noble’s obligation to complete the transactions subject to Noble receiving financing?

No. Noble’s obligation under the merger agreement to complete the transactions is not subject to any condition regarding its ability to finance, or obtain financing for, such transactions.

Q: What happens if the first merger is not completed?

If the merger agreement is not adopted by Diamond Offshore stockholders or if the first merger is not completed for any other reason, Diamond Offshore stockholders will not receive any consideration for their shares of Diamond Offshore common stock. Instead, Diamond Offshore will remain an independent public company, shares of Diamond Offshore common stock will continue to be listed and traded on the NYSE and registered under the Exchange Act and Diamond Offshore will continue to file periodic reports with the SEC. Under specific circumstances, Diamond Offshore may be required to pay Noble a termination fee of $60,000,000. If the merger agreement is terminated by Noble or Diamond Offshore after the special meeting has concluded and Diamond Offshore stockholder approval has not been obtained, Diamond Offshore would be required to pay Noble a no vote termination fee of $16,500,000. See the section titled “The Merger Agreement—Termination of the Merger Agreement” beginning on page 148.

Q: Will the Noble ordinary shares I acquire in the first merger receive a dividend?

After the completion of the first merger and the other transactions, as a holder of Noble ordinary shares, you will receive the same dividends on Noble ordinary shares that all other holders of Noble ordinary shares will receive for any dividend record date that occurs after the completion of the first merger.

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Q: What am I being asked to vote on, and why is this approval necessary?

Diamond Offshore stockholders are being asked to vote on the following proposals:

Approval of the merger agreement proposal by the affirmative vote of holders of a majority of the outstanding shares of Diamond Offshore common stock entitled to vote thereon is required for completion of the first merger. The completion of the first merger is not conditioned on the approval of the advisory compensation proposal or the adjournment proposal.

Q: What vote is required to approve each proposal at the special meeting?

Merger agreement proposal: The affirmative vote of holders of a majority of the outstanding shares of Diamond Offshore common stock entitled to vote thereon is required to approve the merger agreement proposal (the “Diamond Offshore stockholder approval”). Abstentions, a failure to submit a proxy or vote (whether in attendance at the special meeting or not) and broker non-votes will have the same effect as a vote “AGAINST” the merger agreement proposal.

Advisory compensation proposal: The affirmative vote of the holders of a majority in voting power of the votes cast (excluding abstentions and broker non-votes) by the holders of shares present and entitled to vote thereon is required to approve the advisory compensation proposal. An abstention will be counted for purposes of determining whether a quorum is present at the special meeting but not as a vote cast. If a Diamond Offshore stockholder votes to abstain or is not present at the special meeting and does not respond by proxy, it will have no effect on the vote for the advisory compensation proposal (assuming a quorum is present). Broker non-votes will have no effect on the outcome of the vote.

Adjournment proposal: The affirmative vote of the holders of a majority in voting power of the votes cast (excluding abstentions and broker non-votes) by the holders of shares present and entitled to vote thereon is required to approve, if necessary or appropriate, the adjournment proposal. An abstention will be counted for purposes of determining whether a quorum is present at the special meeting but not as a vote cast. If a Diamond Offshore stockholder votes to abstain or is not present at the special meeting and does not respond by proxy, it will have no effect on the vote for the adjournment proposal (assuming a quorum is present). If Diamond Offshore stockholders approve the adjournment proposal, subject to the terms of the merger agreement, Diamond Offshore could adjourn the special meeting and use the additional time to solicit additional proxies, including soliciting proxies from Diamond Offshore stockholders who have previously voted. However, regardless of the results of voting for the adjournment proposal, under the Diamond Offshore bylaws, the chairman of the special meeting may adjourn the special meeting at his or her discretion, subject to the rules and regulations adopted by the Diamond Offshore Board. Diamond Offshore does not intend to call a vote on the adjournment proposal if the merger agreement proposal is approved at the special meeting. Broker non-votes will have no effect on the outcome of the vote.

Q: Is my vote important?

Yes. Your vote is very important. The transactions cannot be completed unless the merger agreement proposal is approved by the affirmative vote of holders of a majority of the outstanding shares of Diamond Offshore

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common stock entitled to vote on the merger agreement proposal. You will also be asked to approve the advisory compensation proposal and the adjournment proposal, both of which are not a condition to the consummation of the transactions. Only Diamond Offshore stockholders as of the close of business on the record date are entitled to vote at the Diamond Offshore special meeting. The Diamond Offshore Board unanimously recommends that the Diamond Offshore stockholders vote “FOR” the merger agreement proposal, “FOR” the advisory compensation proposal and “FOR” the adjournment proposal.

Q: What happens if the advisory compensation proposal is not approved?

Because the vote on advisory compensation proposal is advisory only, it will not be binding on either Diamond Offshore or Noble, and the first merger is not conditioned or dependent upon the approval of the advisory compensation approval. Accordingly, if the merger agreement is adopted and the transactions are completed, the compensation that may be paid or become payable to Diamond Offshore’s named executive officers that is based on or otherwise related to such transactions will be payable to Diamond Offshore’s named executive officers, subject only to the conditions applicable thereto, regardless of the outcome of the vote of Diamond Offshore stockholders on the advisory compensation proposal. However, Diamond Offshore and Noble value the opinions of Diamond Offshore stockholders and Noble expects to consider the outcome of the vote, along with other relevant factors, when considering future executive compensation, assuming the transactions are completed.

Q: Why are Diamond Offshore stockholders being asked to vote on executive officer compensation?

The SEC has adopted rules that require Diamond Offshore to seek a non-binding advisory vote on certain compensation that may be paid or become payable to Diamond Offshore’s named executive officers that is based on or otherwise relates to the transactions. For additional information regarding the advisory compensation proposal, see the section titled “Diamond Offshore Proposals—Non-Binding Advisory Compensation Proposal” beginning on page 160. Diamond Offshore urges its stockholders to read the section entitled “The Transactions—Interests of Directors and Executive Officers of Diamond Offshore in the Transactions” beginning on page 97.

Q: What constitutes a quorum at the special meeting?

A quorum is the minimum number of stockholders necessary to hold a valid meeting. The presence at the special meeting, in person or by proxy, of the holders of issued and outstanding shares of Diamond Offshore common stock representing a majority in voting power and entitled to vote at the meeting constitutes a quorum. If you submit a properly executed proxy card, even if you do not vote for the proposal or vote to “ABSTAIN” in respect of the proposal, your shares of Diamond Offshore common stock will be counted for purposes of calculating whether a quorum is present for the transaction of business at the special meeting. Broker non-votes will not be treated as present for purposes of determining the presence of a quorum at the special meeting. However, because the only proposals for consideration at the special meeting are nondiscretionary proposals, it is not expected that there will be any broker non-votes at the special meeting.

Even if a quorum is present, the special meeting may also be adjourned in order to provide more time to solicit additional proxies in favor of the merger agreement proposal if sufficient votes are cast in favor of the adjournment proposal. Diamond Offshore does not intend to call a vote on the adjournment proposal if the merger agreement proposal is approved at the special meeting.

Q: How does the Diamond Offshore Board recommend that I vote?

The Diamond Offshore Board unanimously recommends that Diamond Offshore stockholders vote “FOR” the merger agreement proposal, “FOR” the advisory compensation proposal and “FOR” the adjournment proposal.

Q: What do I need to do now?

After carefully reading and considering the information contained in this proxy statement/prospectus (including the annexes hereto) and the information incorporated by reference herein, please vote your shares as soon as

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possible so that your shares will be represented at the special meeting. Please follow the instructions set forth on the accompanying proxy card or on the voting instruction form provided by the record holder if your shares are held in the name of your broker, bank or other nominee.

Please do not submit your evidence of ownership at this time.

Please carefully consider the information contained in this proxy statement/prospectus (including the annexes hereto) and the information incorporated by reference herein. Whether or not you plan to attend the special meeting, Diamond Offshore encourages you to submit your proxy to vote via the internet, by telephone or by mail so that your shares will be voted in accordance with your wishes even if you later decide not to attend the special meeting.

Q: How do I vote?

Diamond Offshore Stockholders of Record: Shares Registered in Your Name

If you are a Diamond Offshore stockholder of record, there are several ways for you to vote your shares of Diamond Offshore common stock. Whether or not you plan to attend the special meeting, we urge you to vote using the enclosed proxy card prior to the special meeting to ensure that your vote is counted.

Beneficial Owners: Shares Registered in the Name of a Broker, Bank or Other Agent

If you are a beneficial owner of shares of Diamond Offshore common stock registered in the name of your broker, bank or other agent, you should have received a voting instruction form from that organization rather than directly from us. Please check with your bank, broker or other agent and follow the voting instructions they provide to vote your shares of Diamond Offshore common stock. Generally, you will have three options for returning your proxy.

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If you receive multiple proxy cards from Diamond Offshore or your broker, bank or other agent, this indicates that your shares of Diamond Offshore common stock are held in more than one account, such as two brokerage accounts and are registered in different names. You should complete and return each of the proxy cards to ensure that all of your shares of Diamond Offshore common stock are voted. Unless you revoke your proxy before it is exercised at the special meeting, your shares of Diamond Offshore common stock represented by your proxy will be voted at the special meeting in accordance with the directions given in your proxy.

Q: Who is entitled to vote at the Diamond Offshore special meeting?

The Diamond Offshore Board has fixed July 19, 2024 as the record date for the Diamond Offshore special meeting (the “record date”). All holders of record of shares of Diamond Offshore common stock as of the close of business on the record date are entitled to receive notice of, and to vote at, the Diamond Offshore special meeting. As of the record date, there were 102,911,311 shares of Diamond Offshore common stock issued and outstanding. Attendance at the Diamond Offshore special meeting is not required to vote. Instructions on how to vote your shares by proxy without attending the Diamond Offshore special meeting are provided in this section above.

Q: When and where will the special meeting take place, and how do I attend the special meeting?

The special meeting will be held in the offices of Diamond Offshore located at 777 N. Eldridge Parkway, 12^th floor, Houston, Texas 77079, on [—], 2024, at [—] a.m., Central Time.

You may attend the special meeting in person. Even if you plan to attend the special meeting, Diamond Offshore recommends that you vote your shares of Diamond Offshore common stock in advance as described above so that your vote will be counted if you later decide not to or become unable to attend the special meeting.

Q: What is the difference between holding shares as a stockholder of record and as a beneficial owner?

If your shares of Diamond Offshore common stock are registered directly in your name with the transfer agent of Diamond Offshore, Computershare, Inc., you are considered the stockholder of record with respect to those shares. As the stockholder of record, you have the right to vote or to grant a proxy for your vote directly to Diamond Offshore or to a third party to vote at the special meeting. If your shares of Diamond Offshore common stock are held by a broker, bank or other nominee, you are considered the beneficial owner of shares held in “street name,” and your broker, bank or other nominee is considered the stockholder of record with respect to those shares. Your broker, bank or other nominee will send you, as the beneficial owner, voting instruction forms for you to use in directing the broker, bank or other nominee in how to vote your shares of Diamond Offshore common stock. You should follow the instructions provided therein to vote your shares of Diamond Offshore common stock.

Q: If my shares of Diamond Offshore common stock are held in “street name” by a broker, bank or other nominee, will my broker, bank or other nominee vote my shares of Diamond Offshore common stock for me?

If your shares of Diamond Offshore common stock are held in “street name” in a stock brokerage account or by a broker, bank or other nominee, you must provide the record holder of your shares of Diamond Offshore common stock with instructions on how to vote your shares of Diamond Offshore common stock. Please follow the voting instructions provided by your broker, bank or other nominee. Please note that you may not vote shares held in “street name” by returning a proxy card or voting instruction form directly to Diamond Offshore. Your broker, bank or other nominee is obligated to provide you with a voting instruction form for you to use. You may also cast your vote in person at the special meeting.

Applicable stock exchange rules permit brokers to vote their customers’ stock held in “street name” on routine matters when the brokers have not received voting instructions from their customers. Those rules do not,

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however, allow brokers to vote their customers’ stock held in “street name” on non-routine matters unless they have received voting instructions from their customers. In such cases, the uninstructed shares for which the broker is unable to vote are called broker non-votes. The merger agreement proposal, the advisory compensation proposal and the adjournment proposal are non-routine matters on which brokers are not allowed to vote unless they have received voting instructions from their customers. You must provide voting instructions to your broker for your shares to be voted. Because the only proposals for consideration at the special meeting are nondiscretionary proposals, it is not expected that there will be any broker non-votes at the special meeting. However, if there are any broker non-votes, they will have (i) the same effect as a vote “AGAINST” the merger agreement proposal, (ii) no effect on the advisory compensation proposal (assuming a quorum is present) and (iii) no effect on the adjournment proposal (assuming a quorum is present).

Q: What if I fail to vote or abstain?

For purposes of the special meeting, an abstention occurs when a stockholder attends the special meeting and does not vote or returns a proxy with an “abstain” instruction.

Q: What will happen if I return my proxy card or voting instruction form without indicating how to vote?

If you sign and return your proxy card or voting instruction form without indicating how to vote on any particular proposal, the shares of Diamond Offshore common stock represented by your proxy will be voted as recommended by the Diamond Offshore Board with respect to that proposal. Accordingly, your shares of Diamond Offshore common stock will be voted “FOR” the merger agreement proposal, “FOR” the advisory compensation proposal and “FOR” the adjournment proposal, in accordance with the recommendation of the Diamond Offshore Board.

Q: May I change or revoke my vote after I have delivered my proxy card or voting instruction form?

Yes. If you are a stockholder of record of Diamond Offshore common stock as of the close of business on the record date, whether you submit a proxy by the Internet or mail, you can change or revoke your proxy before it is exercised at the special meeting in one of the following ways:

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If you are a beneficial owner of Diamond Offshore common stock as of the close of business on the record date, you must follow the instructions of your broker, bank or other nominee to revoke or change your voting instructions.

Q: What are the material U.S. federal income tax consequences of the mergers?

The parties intend for the mergers, taken together, to be treated as a tax-free reorganization under Section 368(a) of the Internal Revenue Code of 1986, as amended (the “Code”), and for the mergers not to be subject to Section 367(a)(1) of the Code, except with respect to a five-percent transferee shareholder, if any, as defined in Treasury Regulations Section 1.367(a)-3(c)(5)(ii). Noble and Diamond Offshore intend to report the mergers, taken together, consistent with such treatment.

Assuming the mergers are so treated, a U.S. Holder (as defined in the section entitled “Material Tax Considerations—Material U.S. Federal Income Tax Considerations”) of Diamond Offshore common stock that is not a five-percent transferee shareholder generally will not recognize any realized loss but will recognize any realized gain as a result of the mergers equal to the lesser of (i) the excess, if any, of (A) the sum of the fair market value of Noble ordinary shares (including any fractional share of Noble ordinary shares deemed received and redeemed for cash, as discussed in “Material Tax Considerations—Material U.S. Federal Income Tax Considerations—U.S. federal income tax consequences of the mergers to U.S. Holders”) and the amount of cash consideration (excluding the amount of any cash in lieu of a fractional share of Noble ordinary shares) received by such U.S. Holder pursuant to the first merger over (B) such U.S. Holder’s adjusted tax basis in the Diamond Offshore common stock surrendered pursuant to the first merger and (ii) the amount of cash consideration (excluding the amount of any cash in lieu of a fractional share of Noble ordinary shares) received by such U.S. Holder pursuant to the first merger.

It is not a condition to Noble or Diamond Offshore’s obligations to complete the transactions that the mergers so qualify. None of the parties to the merger agreement have sought or intend to seek any ruling from the IRS regarding the qualification of the mergers as a reorganization within the meaning of Section 368(a) of the Code or the non-application of Section 367(a)(1) of the Code to the mergers. However, in connection with the effectiveness of the registration statement of which this proxy statement/prospectus is a part, Kirkland & Ellis LLP, counsel to Diamond Offshore, will deliver a legal opinion to the effect that the mergers, taken together, will qualify as a “reorganization” within the meaning of Section 368(a) of the Code.

If the mergers qualify as a reorganization, but Section 367(a)(1) of the Code were to apply to the mergers, a U.S. Holder of Diamond Offshore common stock would recognize gain (but not loss) equal to the excess, if any, of (x) the fair market value as of the closing date of any Noble ordinary shares received in the first merger, plus cash received in the first merger, over (y) such U.S. Holder’s tax basis in the Diamond Offshore common stock surrendered in the first merger, as calculated separately for each block of Diamond Offshore common stock held by such U.S. Holder. Any gain so recognized would generally be long-term capital gain if the U.S. Holder held the Diamond Offshore common stock for more than one year at the time the mergers are completed.

For a more complete description of the U.S. federal income tax consequences of the mergers, see the section titled “Material Tax Considerations—Material U.S. Federal Income Tax Considerations” beginning on page 111.

Q: Am I entitled to appraisal rights under the DGCL in connection with the first merger?

Yes. Record holders and beneficial owners of Diamond Offshore common stock who comply with the procedures set forth in Section 262 of the DGCL will be entitled to appraisal rights if the first merger is completed. Under Section 262 of the DGCL, record holders and beneficial owners of shares of Diamond Offshore common stock with respect to which appraisal rights are properly demanded and perfected and not withdrawn or lost are entitled to have such shares of Diamond Offshore common stock appraised by the Delaware Court of Chancery. Shares of Diamond Offshore common stock held by record holders and beneficial owners who properly exercise appraisal rights in

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accordance with Section 262 of the DGCL will not be converted into the right to receive the merger consideration, but instead will be canceled and represent the right to receive, in lieu of the merger consideration, a cash payment that is equal to the fair value of their shares of Diamond Offshore common stock at the effective time (exclusive of any element of value arising from the accomplishment or expectation of the first merger), as determined by the Delaware Court of Chancery, together with interest, if any as determined in accordance with Section 262 of the DGCL. The fair value of such shares of Diamond Offshore common stock could be more than, less than, or equal to the merger consideration. Diamond Offshore is required to send a notice to that effect to each record holder, as of the record date, of Diamond Offshore common stock not less than 20 days prior to the special meeting and include in the notice a copy of Section 262 of the DGCL or information directing the stockholders to a publicly available electronic resource at which Section 262 of the DGCL may be accessed without subscription or cost. This proxy statement/prospectus constitutes Diamond Offshore’s notice to the record holders of Diamond Offshore common stock that appraisal rights are available in connection with the first merger, and the full text of Section 262 of the DGCL may be accessed without subscription or cost at the following publicly available website: https://delcode.delaware.gov/title8/c001/sc09/index.html#262. YOU ARE STRONGLY ENCOURAGED TO CONSULT A LEGAL ADVISOR BEFORE ATTEMPTING TO EXERCISE YOUR APPRAISAL RIGHTS. For more information regarding Diamond Offshore stockholders’ appraisal rights, see the section titled “The Transactions—Appraisal Rights” beginning on page 105.

Q: Do any of the officers or directors of Diamond Offshore have interests in the transactions that may differ from or be in addition to my interests as a Diamond Offshore stockholder?

Yes. In considering the recommendation of the Diamond Offshore Board that Diamond Offshore stockholders vote to approve the merger agreement proposal and the advisory compensation proposal, Diamond Offshore stockholders should be aware that, aside from their interests as stockholders of Diamond Offshore, some of Diamond Offshore’s directors and executive officers have interests in the transactions that may be different from, or in addition to, the interests of Diamond Offshore stockholders generally. The Diamond Offshore Board was aware of and considered these interests, among other matters, in evaluating and negotiating the merger agreement and the transactions, in approving the transactions, and in recommending the approval of the merger agreement proposal and the advisory compensation proposal. For more information and quantification of these interests, please see the section titled “The Transactions—Interests of Directors and Executive Officers of Diamond Offshore in the Transactions” beginning on page 97.

Q: What happens if I sell my shares of Diamond Offshore common stock after the Diamond Offshore record date but before the special meeting?

The Diamond Offshore record date (the close of business on July 19, 2024) is earlier than the date of the special meeting and earlier than the date that the first merger is expected to be completed. If you sell or otherwise transfer your shares of Diamond Offshore common stock after the record date but before the date of the special meeting, you will retain your right to vote at the special meeting. However, you will not have the right to receive the merger consideration in respect of such transferred shares to be received by Diamond Offshore stockholders at the effective time. In order to receive the merger consideration, you must hold your shares of Diamond Offshore common stock through the completion of the first merger.

Q: If I hold Diamond Offshore shares in book-entry or through a Depository Trust Company participant, how will I receive the merger consideration to which I am entitled?

If you are a holder of book-entry shares representing eligible shares of Diamond Offshore common stock (the “Diamond Offshore book-entry shares”) which are held through the Depository Trust Company (“DTC”), the exchange agent will transmit to DTC or its nominees as soon as reasonably practicable after the closing of the transactions, upon surrender of the Diamond Offshore book-entry shares held of record by DTC or its nominees, the whole number of shares of Noble ordinary shares that you have a right to receive pursuant to the merger agreement, the cash consideration and cash in lieu of any fractional Noble ordinary shares and dividends and

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other distributions on the Noble ordinary shares that you have a right to receive pursuant to the merger agreement, in each case, that DTC has the right to receive.

If you are a holder of record of Diamond Offshore book-entry shares which are not held through DTC, the exchange agent will deliver to you, as promptly as practicable after the closing of the transactions, (i) a notice advising you of the effectiveness of the first merger, (ii) a statement reflecting the aggregate whole number of Noble ordinary shares (which will be in uncertificated book-entry form) that you have a right to receive pursuant to the merger agreement and (iii) a check in the amount of U.S. dollars equal to (x) the per share cash consideration plus (y) cash payable in lieu of any fractional Noble ordinary shares and dividends and other distributions on the Noble ordinary shares that you have a right to receive pursuant to the merger agreement.

No interest will be paid or accrued on any amount payable for shares of Diamond Offshore common stock eligible to receive the merger consideration pursuant to the merger agreement.

For additional information on the exchange of Diamond Offshore common stock for the merger consideration, see the section titled “The Merger Agreement—Merger Consideration—Exchange Procedures” beginning on page 123.

Q: Are there any risks that I should consider in deciding whether to vote in favor of the merger agreement proposal?

Yes. You should read and carefully consider the risk factors set forth in the section entitled “Risk Factors” beginning on page 27. You also should read and carefully consider the risk factors of Noble and Diamond Offshore contained in the documents incorporated by reference into this proxy statement/prospectus.

Q: What should I do if I receive more than one set of voting materials?

If you receive multiple proxy cards from Diamond Offshore or your broker, bank or other agent, this usually indicates that your shares of Diamond Offshore common stock are held in more than one account, such as two brokerage accounts and are registered in different names. You should complete and return each of the proxy cards to ensure that all of your shares of Diamond Offshore common stock are voted. Unless you revoke your proxy before it is exercised at the special meeting, your shares of Diamond Offshore common stock represented by your proxy will be voted at the special meeting in accordance with the directions given in your proxy.

Q: Who will solicit and pay the cost of soliciting proxies?

Diamond Offshore has retained Innisfree M&A Incorporated (“Innisfree”) to assist in the solicitation process. Diamond Offshore estimates it will pay Innisfree a base fee of approximately $50,000, in addition to the reimbursement of certain costs and expenses, for these services. Diamond Offshore also has agreed to indemnify Innisfree against various liabilities and expenses that relate to or arise out of its solicitation of proxies (subject to certain exceptions).

Q: What is “householding”?

To reduce the expense of delivering duplicate proxy materials to stockholders who may have more than one account holding a corporation’s common stock but who share the same address, a corporation may adopt a procedure approved by the SEC called “householding.” Under this procedure, certain holders of record who have the same address and last name will receive only one copy of proxy materials until such time as one or more of these stockholders notifies such corporation that they want to receive separate copies. For additional information on “householding,” see the section titled “Householding of Proxy Statement/Prospectus” beginning on page 204.

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Q: Who will tabulate and certify the vote?

The votes at the special meeting will be counted by BetaNXT, Inc. or its affiliates, which will serve as an independent inspector of elections.

Q: Where can I find the voting results of the special meeting?

Within four business days following certification of the final voting results, Diamond Offshore intends to file the final voting results of its special meeting with the SEC in a Current Report on Form 8-K.

Q: Whom should I contact if I have any questions about the proxy materials or voting?

If you have any questions about the proxy materials, or if you need assistance submitting your proxy or voting your shares or need additional copies of this proxy statement/prospectus or the enclosed proxy card, you should contact the proxy solicitation agent for Diamond Offshore, at:

Innisfree M&A Incorporated

501 Madison Avenue, 20th Floor

New York, NY 10022

Diamond Offshore stockholders may call: (877) 750-9497 (TOLL-FREE from the United States and Canada)

or +1 (412) 232-3651 (from other locations)

Banks and brokers may call collect: (212) 750-5833

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CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

This proxy statement/prospectus includes “forward-looking statements” within the meaning of U.S. federal securities laws, including Section 27A of the Securities Act and Section 21E of the Exchange Act. You can identify these statements and other forward-looking statements in this document by words such as “expects,” “continue,” “focus,” “intends,” “anticipates,” “plans,” “targets,” “poised,” “advances,” “drives,” “aims,” “forecasts,” “believes,” “approaches,” “seeks,” “schedules,” “estimates,” “positions,” “pursues,” “progress,” “may,” “can,” “could,” “should,” “will,” “budgets,” “possible,” “outlook,” “trends,” “guidance,” “commits,” “on track,” “objectives,” “goals,” “projects,” “strategies,” “opportunities,” “potential,” “ambitions,” “aspires” and similar expressions, and variations or negatives of these words, but not all forward-looking statements include such words. Forward-looking statements by their nature address matters that are, to different degrees, uncertain such as statements about the consummation of the transactions, including the expected time period to consummate the transactions, and the anticipated benefits (including synergies and free cash flow accretion) of the transactions and planned dividends. All such forward-looking statements are based upon current plans, estimates, expectations and ambitions that are subject to risks, uncertainties and assumptions, many of which are beyond the control of Noble and Diamond Offshore, that could cause actual results to differ materially from those expressed in such forward-looking statements. Key factors that could cause actual results to differ materially include, but are not limited to:

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These forward-looking statements reflect Noble’s and Diamond Offshore’s current views with respect to future events and are based on numerous assumptions and assessments made by Noble and Diamond Offshore in light of their experience and perception of historical trends, current conditions, business strategies, operating environments, future developments and other factors they believe appropriate. By their nature, forward-looking statements involve known and unknown risks and uncertainties because they relate to events and depend on circumstances that will occur in the future. The factors described in the context of such forward-looking statements in this document could cause Noble’s and Diamond Offshore’s plans with respect to the transactions,

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actual results, performance or achievements, industry results and developments to differ materially from those expressed in or implied by such forward-looking statements. Although it is believed that the expectations reflected in such forward-looking statements are reasonable, no assurance can be given that such expectations will prove to have been correct and persons reading this document are therefore cautioned not to place undue reliance on these forward-looking statements which speak only as of the date of this proxy statement/prospectus or, in the case of the information incorporated by reference herein, as of the date of such document. Neither Noble nor Diamond Offshore assumes any obligation to update the information contained in this document (whether as a result of new information, future events or otherwise), except as required by applicable law. With respect to Noble’s capital allocation policy, distributions to shareholders in the form of either dividends or share buybacks are subject to the assessment of the Board of Directors of Noble (the “Noble Board”) of factors such as business development, growth strategy, current leverage and financing needs. There can be no assurance that a dividend will be declared or continued.

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RISK FACTORS

In addition to the other information included in or incorporated by reference into this proxy statement/prospectus (including the annexes hereto), including, among others, the matters addressed in the section entitled “Cautionary Note Regarding Forward-Looking Statements,” Diamond Offshore stockholders should carefully consider the following risk factors before deciding whether to vote for the merger agreement proposal. In addition, you should read and consider the risks associated with each of the businesses of Diamond Offshore and Noble because these risks will relate to Noble following the completion of the transactions. Descriptions of some of these risks can be found in Noble’s and Diamond Offshore’s respective Annual Reports on Form 10-K for the fiscal year ended December 31, 2023, and any amendments thereto, as such risks may be updated or supplemented in each company’s subsequently filed Quarterly Reports on Form 10-Q or Current Reports on Form 8-K, which are incorporated by reference into this proxy statement/prospectus. You should also consider the other information in this proxy statement/prospectus (including the annexes hereto) and the other documents incorporated by reference into this proxy statement/prospectus. See the section titled “Where You Can Find More Information” beginning on page 205.

Risks Related to the Transactions

The exchange ratio is fixed and will not be adjusted in the event of fluctuations in the market price of Noble ordinary shares or shares of Diamond Offshore common stock.

Upon completion of the first merger, each share of Diamond Offshore common stock will be converted into the right to receive $5.65 in cash (as such amount of cash may potentially be adjusted, see the section titled “The Merger Agreement—Merger Consideration—Effects of the Mergers” beginning on page 122), without interest, and 0.2316 of validly issued, fully paid and non-assessable Noble ordinary shares. This exchange ratio is fixed in the merger agreement and will not be adjusted for changes in the market price of either Noble ordinary shares or Diamond Offshore common stock between the date of the merger agreement and the effective time. Due to the fixed exchange ratio, fluctuations in the price of Noble ordinary shares will drive corresponding changes in the value of the merger consideration payable to each Diamond Offshore stockholder. As a result, changes in the price of Noble ordinary shares prior to the completion of the first merger will affect the market value that Diamond Offshore stockholders will become entitled to receive at the effective time. Changes in the price of Noble ordinary shares or Diamond Offshore common stock could result from changes in the business, operations or prospects of Noble or Diamond Offshore prior to or following the completion of the first merger, regulatory considerations, general market and economic conditions and other factors both within and beyond the control of Noble or Diamond Offshore, including, among other things, a decline in the price of oil or gas, a reduction in demand for oil and gas products, increased regulation of drilling and production and a number of other factors beyond the companies’ control that are more fully described in the risk factors sections included in Noble’s and Diamond Offshore’s respective Annual Reports on Form 10-K for the fiscal year ended December 31, 2023, each of which is filed with the SEC and incorporated by reference into this proxy statement/prospectus.

The price of Noble ordinary shares has fluctuated during the period between the date of the merger agreement and the date of this proxy statement/prospectus, and may continue to change through the date of the special meeting and the date that the first merger is completed. For example, based on the range of closing prices of Noble ordinary shares and shares of Diamond Offshore common stock during the period from June 7, 2024, the last full trading day before the public announcement of the transactions, through July 17, 2024, the last practicable trading date before the date of this proxy statement/prospectus, the implied merger consideration to be received by Diamond Offshore stockholders ranged from a high of $16.70 to a low of $15.52 for each share of Diamond Offshore common stock. The actual market value of the Noble ordinary shares received by holders of Diamond Offshore common stock upon completion of the first merger may be outside this range.

The transactions may be completed a considerable period of time after the date of the special meeting. Therefore, at the time of the special meeting, Diamond Offshore stockholders will not know with certainty the value of the

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Noble ordinary shares that they will receive upon completion of the first merger. It is possible that, at the time of the closing of the first merger, the shares of Diamond Offshore common stock held by Diamond Offshore stockholders may have a greater market value than the cash and the Noble ordinary shares for which they are exchanged.

The transactions are subject to conditions, some or all of which may not be satisfied or completed on a timely basis, or at all. The merger agreement may be terminated in accordance with its terms if such conditions are not completed.

The completion of the transactions is subject to a number of conditions, including, among others, (i) the receipt of the Diamond Offshore stockholder approval, (ii) the receipt of any regulatory approvals required to consummate the first merger, (iii) the absence of any order or law prohibiting consummation of the transactions, (iv) the absence of any material adverse effect (as defined in the section titled “The Merger Agreement—Representations and Warranties” beginning on page 142) on Diamond Offshore or Noble since the date of the merger agreement, (v) the effectiveness of the registration statement of which this proxy statement/prospectus forms a part and (vi) the authorization for listing on the NYSE of the Noble ordinary shares to be issued in connection with the first merger. These conditions make the completion and timing of the transactions uncertain. For a more detailed discussion regarding conditions to the transactions, see the section titled “The Merger Agreement—Conditions to Completion of the Transactions” beginning on page 145.

In addition, if the transactions are not completed by June 9, 2025, or, in certain instances, on or before June 9, 2026, either Noble or Diamond Offshore may choose not to proceed with the transactions by terminating the merger agreement, and the parties can mutually decide to terminate the merger agreement at any time. Further, either Noble or Diamond Offshore may elect to terminate the merger agreement in certain other circumstances, as further described in the section titled “The Merger Agreement—Termination of the Merger Agreement” beginning on page 148.

Failure to complete the transactions in a timely manner or at all could have adverse effects on the market value, trading price and/or the future business results and financial condition of Diamond Offshore and Noble.

If the transactions are not completed, the ongoing business, financial condition, financial results and stock price of Diamond Offshore and/or Noble may be adversely affected. Without realizing any of the benefits of having completed the transactions, Noble and/or Diamond Offshore may be subject to a number of risks, including the following:

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The materialization of any of these risks could adversely impact Noble’s and Diamond Offshore’s respective ongoing businesses, financial condition, financial results and the price of Noble ordinary shares or Diamond Offshore common stock. Similarly, delays in the completion of the transactions could, among other things, result in additional transaction costs, loss of revenue or other negative effects associated with uncertainty about completion of the transactions.

The merger agreement contains provisions that limit Diamond Offshore’s ability to pursue alternatives to the transactions, which could discourage a potential competing acquiror of Diamond Offshore from making a favorable alternative proposal and, in specified circumstances, could require Diamond Offshore to pay a termination fee to Noble.

The merger agreement contains certain provisions that restrict Diamond Offshore’s ability to initiate, solicit, knowingly encourage or knowingly facilitate or, subject to certain exceptions, engage in, discussions or negotiations with respect to, or, subject to certain exceptions, approve or recommend, any alternative proposal. Further, even if the Diamond Offshore Board withdraws or qualifies its recommendation with respect to the adoption of the merger agreement, unless the merger agreement has been terminated in accordance with its terms, Diamond Offshore will still be required to hold the special meeting for the purpose of obtaining the Diamond Offshore stockholder approval. See the section titled “The Merger Agreement—Covenants and Agreements—The Special Meeting” beginning on page 135. In addition, Noble generally has an opportunity to offer to modify the terms of the transactions in response to any alternative proposal before the Diamond Offshore Board may withdraw or qualify its recommendation to adopt the merger agreement or otherwise terminate the merger agreement. See the section titled “The Merger Agreement—Covenants and Agreements—No Solicitation” beginning on page 132.

In any of the circumstances described in the section titled “The Merger Agreement—Termination Fees” beginning on page 149, upon termination of the merger agreement, Diamond Offshore would be required to pay a termination fee of $60,000,000 to Noble. If the merger agreement is terminated by Noble or Diamond Offshore after the special meeting has concluded and the Diamond Offshore stockholder approval has not been obtained, Diamond Offshore would be required to pay Noble a no-vote termination fee of $16,500,000. See the section titled “The Merger Agreement—Termination of the Merger Agreement” beginning on page 148.

While the Diamond Offshore Board concluded these obligations were reasonable and customary under the circumstances and would not unduly deter any other party that may be interested in acquiring Diamond Offshore, these provisions could discourage a potential third-party acquiror or merger partner that might have an interest in acquiring all or a significant portion of Diamond Offshore or pursuing an alternative proposal from considering or proposing such an alternative proposal, even if such third-party acquiror or merger partner were prepared to pay consideration with a higher per share implied value than the per share implied value of the merger consideration. In particular, the termination fee, if applicable, could result in a potential third-party acquiror or merger partner proposing to pay consideration with a lower per share implied value to the Diamond Offshore stockholders than it might otherwise have proposed to pay absent such termination fee.

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If the merger agreement is terminated and Diamond Offshore determines to seek another business combination, Diamond Offshore may not be able to negotiate a transaction with another party on terms comparable to, or better than, the terms of the merger agreement.

The transactions are subject to the requirements of the HSR Act and other regulatory approvals, and regulatory authorities may impose conditions that could have an adverse effect on Noble and/or Diamond Offshore following the transactions or that could delay, prevent or increase the costs associated with completion of the transactions.

Before the transactions may be completed, the applicable waiting period (including any extensions thereof) under the provisions of the HSR Act must have expired or been terminated and all other required regulatory clearance or approvals must be obtained. In deciding whether to grant the required approvals, consents, registrations, permits, expirations or terminations of waiting periods, authorizations or other confirmations, the relevant governmental entities from which these approvals are required have broad discretion in administering applicable laws and may take into account various facts and circumstances in their consideration of the transactions, including other potential transactions in the business and industries in which Diamond Offshore and Noble participate. These governmental entities may be affected by government shutdowns, which could result in delays regarding any potential approvals or other actions, or other changes in the regulatory or legislative landscape. These governmental entities may at their discretion initiate proceedings seeking to prevent, or otherwise seek to prevent, the transactions. As a condition to the approval of the transactions, these governmental entities also may seek to impose requirements, limitations or costs or place restrictions on the conduct of Diamond Offshore’s business or Noble’s business following the transactions. Under the merger agreement, each of Noble and Diamond Offshore has agreed to use its reasonable best efforts to take all actions, and to do and to assist and cooperate with the other parties in doing, all things necessary, proper or advisable under applicable laws to consummate and make effective the mergers and the other transactions.

Other governmental agencies, bodies, authorities or entities may also impose conditions, terms, obligations, requirements, limitations, costs, divestitures or other restrictions in connection with their approval of or consent to the transactions, and such conditions, terms, obligations, requirements, limitations, costs, divestitures or other restrictions may delay completion of the transactions or impose additional material costs on or materially limit Noble’s revenues following the completion of the transactions. There can be no assurance that governmental agencies, bodies, authorities or entities will choose not to impose such conditions, terms, obligations, requirements, limitations, costs, divestitures or other restrictions, and, if imposed, such conditions, terms, obligations or restrictions may delay or lead to the abandonment of the transactions. At any time before or after consummation of the transactions, any governmental entity of competent jurisdiction could take such action under regulatory laws as it deems necessary or desirable in the public interest, including seeking to enjoin the completion of the transactions, seeking to place limitations or obligations on the commercial activities of Noble or Diamond Offshore or seeking the divestiture of substantial assets of Noble or Diamond Offshore or their respective subsidiaries.

However, notwithstanding each party’s commitment to use such reasonable best efforts, Noble is not required to take any actions or agree to any such remedies if doing so would have, or be expected to have, individually or in the aggregate, a material adverse effect on Noble, defined by reference to certain parameters specified in the merger agreement, including, subject to the following sentence, any such requirements, limitations costs, divestitures or other restrictions. Diamond Offshore and Noble have agreed that any action or agreement to any such remedy that would, or would reasonably be expected to, result in the sale, disposition or other disposal of any drillship will be deemed for the purposes described in the foregoing sentence to have a material adverse effect on Noble. See the section titled “The Merger Agreement—Covenants and Agreements—Regulatory Efforts” beginning on page 137.

In addition, the special meeting may take place before certain required regulatory approvals have been obtained and, therefore, before the terms on which such required regulatory approvals may be obtained, or the conditions to obtaining such regulatory approvals that may be imposed, are known. As a result, if Diamond Offshore

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stockholders approve the first merger at the special meeting, Noble and Diamond Offshore may make decisions after the special meeting to waive a condition as to the receipt of certain required regulatory approvals or to take certain actions required to obtain such approvals without seeking further stockholder approval, and such actions could have an adverse effect on Noble following the completion of the transactions.

For a more detailed description of the regulatory review process, see the section titled “The Transactions—Regulatory Approvals Required for the Transactions” beginning on page 103.

Any delay in completing the transactions may substantially reduce the benefits expected to be obtained from the transactions.

In addition to obtaining the required governmental clearances and approvals, the transactions are subject to a number of other conditions beyond the control of Noble and Diamond Offshore that may delay or otherwise materially adversely affect its completion. See the risk factor titled “—Failure to complete the transactions in a timely manner or at all could have adverse effects on the market value, trading price and/or the future business results and financial condition of Diamond Offshore and Noble.” Noble and Diamond Offshore cannot predict when the conditions required to complete the transactions will be satisfied. Any delay in completing the transactions may materially adversely affect the synergies, including the anticipated annual pre-tax cost synergies of approximately $100 million, and other benefits that Noble and Diamond Offshore expect to achieve if the transactions and the integration of their respective businesses are completed within the expected time frame.

Members of the Diamond Offshore Board and management have interests in the transactions that are different from, or in addition to, those of other stockholders.

In considering whether to adopt the merger agreement and approve the transactions, Diamond Offshore stockholders should recognize that members of the Diamond Offshore Board and management have interests in the transactions that differ from, or are in addition to, their interests as stockholders of Diamond Offshore.

The executive officers of Diamond Offshore have arrangements with Diamond Offshore that provide for certain severance payments or benefits, accelerated vesting of certain equity-based awards and other rights and other payments or benefits upon completion of the transactions, and/or if their employment or service is terminated under certain circumstances between the date of the merger agreement and the effective time and following the completion of the transactions. The executive officers and directors of Diamond Offshore also have rights to indemnification, advancement of expenses and directors’ and officers’ liability insurance that will survive the completion of the transactions. In addition, prior to the effective time of the second merger, Noble has agreed to take all necessary actions to cause the Noble Board, as of the effective time, to be increased by one director and to cause one individual who is, as of the date of the merger agreement, serving on the Diamond Offshore Board and mutually agreed by Diamond Offshore and Noble, to be appointed to the Noble Board immediately following the effective time. The Diamond Offshore Board was aware of these interests and considered them, among other matters, in approving the merger agreement and making its recommendation that the Diamond Offshore stockholders vote “FOR” the merger agreement proposal and “FOR” the advisory compensation proposal.

These interests are further described in “The Transactions—Interests of Directors and Executive Officers of Diamond Offshore in the Transactions” beginning on page 97.

Each party is subject to business uncertainties and contractual restrictions while the proposed transactions are pending, which could adversely affect each party’s respective business and operations.

In connection with the pendency of the transactions, it is possible that some customers, suppliers and other persons with whom Noble or Diamond Offshore has a business relationship may delay or defer certain business decisions or might decide to seek to terminate, change or renegotiate their relationships with Noble or Diamond Offshore, as the case may be, as a result of the pendency of the transactions. In addition, the merger agreement restricts each company, without the other’s consent, from making certain acquisitions and taking other specified

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actions until the transactions close or the merger agreement terminates. For example, during the pendency of the transactions, Diamond Offshore cannot sell, in the aggregate, material properties or assets having a fair market value in excess of $25 million and Noble cannot sell, in the aggregate, material properties or assets, in each case, consisting of floater rigs having a fair market value in excess of $400 million, in each case subject to exceptions specified in the merger agreement. These restrictions may prevent Diamond Offshore or Noble from pursuing otherwise attractive business opportunities and making other changes to their respective businesses before completion of the transactions or termination of the merger agreement. See the section titled “The Merger Agreement—Covenants and Agreements—Conduct of Business” beginning on page 126.

The Diamond Offshore Board has not requested, and does not anticipate requesting, an updated opinion from its financial advisors reflecting changes in circumstances that may have occurred since the signing of the merger agreement.

The Diamond Offshore Board has received an opinion from each of its financial advisors dated June 9, 2024 in connection with the Diamond Offshore Board’s evaluation of the transactions. The Diamond Offshore Board has not requested, and does not anticipate requesting, an updated opinion from each of its financial advisors reflecting changes in circumstances that may have occurred since the signing of the merger agreement. As a result, the Diamond Offshore Board will not receive an updated, revised or reaffirmed opinion from each of its financial advisors prior to the consummation of the transactions. Changes in the operations and prospects of Noble or Diamond Offshore, general market and economic conditions and other factors that may be beyond the control of Diamond Offshore or Noble, may significantly alter the value of Noble or Diamond Offshore or the prices of Noble ordinary shares or of the shares of Diamond Offshore common stock by the time the transactions are completed. The opinions of each of Diamond Offshore’s financial advisors speak as of the date each such opinion was rendered, and do not speak as of the time the transactions will be completed nor as of any date other than the date of each such opinion. Because the Diamond Offshore Board does not anticipate requesting its financial advisors to update their respective opinions, the opinions will not address the fairness of the merger consideration, from a financial point of view, at the time the transactions are consummated. The Diamond Offshore Board recommendation that Diamond Offshore stockholders vote “FOR” the merger agreement proposal, the advisory compensation proposal and the adjournment proposal, however, is made as of the date of this proxy statement/prospectus.

For a description of the opinions that Diamond Offshore received from its financial advisors, see the section titled “The Transactions—Opinions of Diamond Offshore’s Financial Advisors” beginning on page 68. Copies of the respective opinions of Diamond Offshore’s financial advisors are attached as Annex B and Annex C, respectively, to this proxy statement/prospectus.

Uncertainties associated with the transactions may cause a loss of management personnel and other key employees, and Noble and Diamond Offshore may be unable to attract or retain management personnel and other key employees during the pendency of the transactions, which could adversely affect the future business and operations of Noble after the completion of the transactions.

Noble and Diamond Offshore are dependent on the experience and industry knowledge of their respective management personnel and other key employees to execute their business plans. The success of Noble after the completion of the transactions will depend in part upon the ability of Noble and Diamond Offshore to attract, motivate and retain key management personnel and other key employees. In connection with the pending transactions, Noble’s and Diamond Offshore’s current and prospective employees may experience uncertainty about their future roles with Noble following completion of the transactions, which may materially adversely affect Noble’s and Diamond Offshore’s ability to attract, motivate and retain management personnel and other key employees during the pendency of the transactions. Furthermore, Noble and Diamond Offshore may incur costs in their efforts to retain management personnel and other key employees prior to and after the completion of the transactions. Key employees may depart because of issues relating to the uncertainty and difficulty of integration or a desire not to remain with Noble following completion of the transactions. Accordingly, no assurance can be given that Noble and Diamond Offshore will be able to retain management personnel and other key employees to the same extent that Noble and Diamond Offshore have been able to in the past.

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Potential litigation against Noble and Diamond Offshore could result in substantial costs, an injunction preventing the completion of the transactions and/or a judgment resulting in the payment of damages.

Securities class action lawsuits and derivative lawsuits are often brought against public companies that have entered into merger agreements. Even if such a lawsuit is unsuccessful, defending against these claims can result in substantial costs. An adverse judgment could result in monetary damages, which could have a negative impact on Noble’s and Diamond Offshore’s respective liquidity and financial condition.

Stockholders of Diamond Offshore may file lawsuits against Noble, Diamond Offshore and/or the directors and officers of either company in connection with the transactions. These lawsuits could prevent or delay the completion of the transactions and result in significant costs to Diamond Offshore and/or Noble, including any costs associated with the indemnification of directors and officers. There can be no assurance that any of the defendants will be successful in the outcome of any potential lawsuits.

Additionally, if a plaintiff is successful in obtaining an injunction prohibiting completion of the transactions, then that injunction may delay or prevent the transactions from being completed, or from being completed within the expected time frame, which may adversely affect Noble’s and Diamond Offshore’s respective business, financial position and results of operation. Currently, neither Noble nor Diamond Offshore is aware of any securities class action lawsuits or derivative lawsuits having been filed in connection with the transactions.

See the section titled “The Transactions—Litigation Relating to the Transactions” beginning on page 110 for a description of demand letters that were sent by purported stockholders of Diamond Offshore in connection with the transactions as of July 19, 2024.

Completion of the transactions may trigger change in control or other provisions in certain agreements to which Diamond Offshore is a party, which may have an adverse impact on Noble’s business and results of operations after completion of the transactions.

The completion of the transactions may trigger change in control and other provisions in certain agreements to which Diamond Offshore is a party. If Noble and Diamond Offshore are unable to negotiate waivers of those provisions, the counterparties may exercise their rights and remedies under the agreements, potentially terminating the agreements or seeking monetary damages. Even if Noble and Diamond Offshore are able to negotiate waivers, the counterparties may require a fee for such waivers or seek to renegotiate the agreements on terms less favorable to Diamond Offshore or Noble following the transactions, including the first merger and the second merger.

The Noble ordinary shares to be received by Diamond Offshore stockholders upon completion of the first merger will have different rights from shares of Diamond Offshore common stock due to the difference between Delaware law and English law.

Upon completion of the first merger, Diamond Offshore stockholders will no longer be stockholders of Diamond Offshore but will instead become shareholders of Noble, and their rights as Noble shareholders will be governed by English law, including the Companies Act 2006 of the United Kingdom and, the terms of Noble’s amended and restated memorandum and articles of association (“Noble’s articles”). The terms of Noble’s articles are in some respects materially different than the terms of the Fourth Amended and Restated Certificate of Incorporate of Diamond Offshore (the “Diamond Offshore charter”), and the Third Amended and Restated Bylaws of Diamond Offshore (the “Diamond Offshore bylaws”), which currently govern the rights of Diamond Offshore stockholders.

It may be difficult for shareholders of Noble (including former Diamond Offshore stockholders that become shareholders of Noble upon completion of the first merger) to effect service of process on Noble or its directors or officers in the United States or to enforce in the United States judgments obtained in U.S. courts against Noble or its officers or directors based on the civil liability provisions of the U.S. securities laws or otherwise. Even if a shareholder of Noble is successful in bringing an action of this kind, English law (or any other applicable law)

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may render such shareholder of Noble unable to enforce a judgment against Noble’s assets or the assets of its directors and executive officers. In addition, it is doubtful whether English courts would enforce certain civil liabilities under U.S. securities laws in original actions or judgments of U.S. courts based upon these civil liability provisions. In addition, awards of punitive damages in actions brought in the United States or elsewhere may be unenforceable in the United Kingdom. An award for monetary damages under the U.S. securities laws would likely be considered punitive if it does not seek to compensate the claimant for loss or damage suffered and is intended to punish the defendant. The enforceability of any judgment in the United Kingdom will depend on the particular facts of the case as well as the laws and treaties in effect at the time. The United States and the United Kingdom do not currently have a treaty providing for recognition and enforcement of judgments (other than arbitration awards) in civil and commercial matters. As a result of the above, holders of Noble ordinary shares may have more difficulty in protecting their interest through actions against Noble’s management, directors or major shareholders than they would as stockholders of Diamond Offshore common stock.

See the section titled “Comparison of Rights of Shareholders of Noble and Stockholders of Diamond Offshore” beginning on page 172 for a discussion of the different rights associated with shares of Diamond Offshore common stock and Noble ordinary shares.

Noble or Diamond Offshore may waive one or more of the closing conditions without re-soliciting stockholder approval.

The consummation of the transactions is subject to the satisfaction or waiver of certain conditions. Noble and/or Diamond Offshore may determine to waive, in whole or in part as permitted by applicable law, one or more of the conditions to closing the transactions prior to Noble or Diamond Offshore, as the case may be, being obligated to consummate the transactions. Each of Noble and Diamond Offshore currently expects to evaluate the materiality of any waiver and its effect on its respective stockholders in light of the facts and circumstances at the time and to determine whether any amendment of this proxy statement/prospectus or any re-solicitation of proxies is required in light of such waiver. Any determination whether to waive any condition to the transactions, amend or supplement this proxy statement/prospectus as a result of a waiver or, in the case of Diamond Offshore, re-solicit stockholder approval, will be made by Noble or Diamond Offshore at the time of such waiver based on the facts and circumstances as they exist at that time.

Diamond Offshore stockholders will have a significantly reduced ownership and voting interest after the first merger and will exercise less influence over the policies of Noble following completion of the first merger than they now have on the policies of Diamond Offshore.

Noble shareholders currently have the right to vote in the election of the Noble Board and on other matters affecting Noble. Diamond Offshore stockholders currently have the right to vote in the election of the Diamond Offshore Board and on other matters affecting Diamond Offshore. Immediately after the transactions are completed, it is expected that holders of Noble ordinary shares immediately prior to the consummation of the first merger will own approximately 85% of outstanding fully diluted Noble ordinary shares, and former holders of Diamond Offshore common stock and Diamond Offshore equity awards immediately prior to the consummation of the first merger will own approximately 15% of outstanding fully diluted Noble ordinary shares, in each case based on closing prices of Noble ordinary shares and shares of Diamond Offshore common stock as of July 17, 2024, the last practicable date before the date of this proxy statement/prospectus. As a result, current Diamond Offshore stockholders will have significantly less influence on the policies of Noble than they now have on the policies of Diamond Offshore.

Risks Related to Noble After Completion of the Transactions

Noble may not achieve the intended benefits and the transactions may disrupt its current plans or operations.

There can be no assurance that Noble will be able to successfully integrate Diamond Offshore’s assets or otherwise realize the expected benefits of the transactions (including annual pre-tax cost synergies). Difficulties in integrating Diamond Offshore into Noble may result in Noble performing differently than expected, in

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operational challenges or in the failure to realize anticipated synergies and efficiencies in the expected time frame or at all, including annual pre-tax cost synergies of approximately $100 million, in which case the transactions may not be accretive to earnings per share, may not improve Noble’s balance sheet position, may not enhance Noble’s ability to delever and may not generate additional free cash flow. The integration of the two companies may result in material challenges, including the diversion of management’s attention from ongoing business concerns; retaining key management and other employees; retaining or attracting business and operational relationships; the possibility of faulty assumptions underlying expectations regarding the integration process and associated expenses; consolidating corporate and administrative infrastructures and eliminating duplicative operations; coordinating geographically separate organizations; unanticipated issues in integrating information technology, communications and other systems; as well as potential unknown liabilities, unforeseen expenses relating to integration, or delays associated with the acquisition. See the section titled “Cautionary Note Regarding Forward-Looking Statements” beginning on page 24.

The combined company’s results may suffer if it does not effectively manage its expanded operations following the merger.

Following completion of the transactions, the combined company’s success will depend, in part, on Noble’s ability to manage the expansion resulting from the transactions, which poses numerous risks and uncertainties, including the need to integrate the operations and business of Diamond Offshore into its existing business in an efficient and timely manner, to combine systems and management controls and to integrate relationships with industry contacts and business partners.

The anticipated benefits and cost savings of the merger may not be realized fully or at all, may take longer to realize than expected or could have other adverse effects that Noble does not currently foresee. Some of the assumptions that Noble has made, such as the achievement of pre-tax cost synergies of approximately $100 million, may not be realized, in which case the transactions may not be accretive to earnings per share, may not improve Noble’s balance sheet position, may not enhance Noble’s ability to delever and may not generate additional free cash flow. There could also be unknown liabilities and unforeseen expenses associated with the transactions that were not discovered in the due diligence review conducted by each company prior to entering into the merger agreement.

The market price of Noble ordinary shares after completion of the first merger may be affected by factors different from those affecting the price of Noble ordinary shares or Diamond Offshore common stock before the completion of the transactions.

Upon completion of the first merger, holders of Noble ordinary shares and Diamond Offshore common stock will be holders of Noble ordinary shares. As the businesses of Noble and Diamond Offshore are different, the results of operations as well as the price of Noble ordinary shares may in the future be affected by factors different from those factors affecting Noble and Diamond Offshore as independent standalone companies. Following completion of the transactions, Noble will face additional risks and uncertainties that Noble or Diamond Offshore may currently not be exposed to as independent companies.

The market price of Noble ordinary shares may decline as a result of completing the transactions.

The market price of Noble ordinary shares may decline as a result of completing the transactions if, among other things, it is unable to achieve the expected benefits and synergies of the transactions, if the transactions are not completed within the anticipated timeframe or if the costs related to the transactions are greater than expected. The market price of Noble ordinary shares also may decline if Noble does not achieve the perceived benefits and expected synergies of the transactions as rapidly or to the extent anticipated by financial or industry analysts or if the effect of the transactions on Noble’s financial position, results of operations or cash flows is not consistent with the expectations of financial or industry analysts.

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The completion of the transactions may result in a loss of customers, distributors, suppliers, vendors, landlords and other business partners and may result in the termination of existing contracts.

Following the completion of the transactions, some of the customers, distributors, suppliers, vendors, landlords and other business partners of Diamond Offshore may terminate or scale back their current or prospective business relationships with Noble. Some customers may not wish to source a larger percentage of their needs from a single company or may feel that Noble is too closely allied with one of their competitors. In addition, Diamond Offshore has contracts with customers, landlords and other business partners that may require it to obtain consents from these other parties in connection with the transactions, which may not be obtained on favorable terms or at all. If relationships with customers, distributors, suppliers, vendors, landlords and other business partners are adversely affected by the transactions, or if Noble, following completion of the transactions, loses the benefits of certain contracts of Diamond Offshore, Noble’s business and financial performance could suffer.

The combined company may record goodwill and other intangible assets that could become impaired and result in material non-cash charges to the results of operations of the combined company in the future.

The transactions will be accounted for as an acquisition by Noble in accordance with Generally Accepted Accounting Principles (“GAAP”). Under the acquisition method of accounting, the assets and liabilities of Diamond Offshore and its subsidiaries will be recorded, as of completion, at their respective fair values and added to those of Noble. The reported financial condition and results of operations of Noble for periods after completion of the transactions will reflect Diamond Offshore balances and results after completion of the transactions but will not be restated retroactively to reflect the historical financial position or results of operations of Diamond Offshore and its subsidiaries for periods prior to the transactions. For additional information, see the section titled “Unaudited Pro Forma Condensed Combined Financial Information of Noble” beginning on page 40.

Under the acquisition method of accounting, the total purchase price will be allocated to Diamond Offshore’s tangible assets and liabilities and identifiable intangible assets based on their fair values as of the date of completion of the transactions. The excess of the purchase price over those fair values will be recorded as goodwill. Noble and Diamond Offshore expect that the transactions may result in the creation of goodwill based upon the application of the acquisition method of accounting. To the extent goodwill or intangibles are recorded and the values become impaired, the combined company may be required to recognize material non-cash charges relating to such impairment. The combined company’s operating results may be significantly impacted from both the impairment and the underlying trends in the business that triggered the impairment.

Noble and Diamond Offshore will incur direct and indirect costs as a result of the transactions, which may be in excess of those anticipated by Noble or Diamond Offshore.

Noble and Diamond Offshore will incur substantial expenses in connection with completing the transactions, and Noble also expects to incur substantial expenses in connection with coordinating the businesses, operations, policies and procedures of Noble and Diamond Offshore over a period of time following the completion of the transactions. While Noble and Diamond Offshore have assumed that a certain level of transaction and coordination expenses will be incurred, there are a number of factors beyond Noble’s and Diamond Offshore’s control that could affect the total amount or the timing of these transaction and coordination expenses. Many of the expenses that will be incurred, by their nature, are difficult to estimate accurately. These expenses may exceed the costs historically borne by Noble and Diamond Offshore.

The unaudited pro forma condensed combined financial information in this proxy statement/prospectus is presented for illustrative purposes only and may not be reflective of the operating results and financial condition of the combined company following completion of the transactions.

The unaudited pro forma condensed combined financial information in this proxy statement/prospectus is presented for illustrative purposes only and is not necessarily indicative of what Noble’s actual financial position

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or results of operations would have been had the transactions been completed on the dates indicated. Further, Noble’s actual results and financial position after the transactions may differ materially and adversely from the unaudited pro forma condensed combined financial information that is included in this proxy statement/prospectus. The unaudited pro forma condensed combined financial information has been prepared with the expectation, as of the date of this proxy statement/prospectus, that Noble will be identified as the acquirer under GAAP and reflects adjustments based upon preliminary estimates of the fair value of assets to be acquired and liabilities to be assumed. The final acquisition accounting will be based upon the actual purchase price and the fair value of the assets and liabilities of the party that is determined to be the acquiree under GAAP as of the date of the completion of the transactions. In addition, subsequent to the closing date, there will be further refinements of the acquisition accounting as additional information becomes available. Accordingly, the final acquisition accounting may differ materially from the pro forma condensed combined financial information reflected in this document. See the section titled “Unaudited Pro Forma Condensed Combined Financial Information of Noble” beginning on page 40 for more information.

The forecasted financial information presented in this proxy statement/prospectus may not be an indication of the actual results of the transactions or Noble’s future results following the transactions.

This proxy statement/prospectus contains forecasted financial information consisting of the Diamond Offshore forecasted financial information prepared by Diamond Offshore management, the Diamond Offshore adjusted Noble forecasted financial information prepared by Noble management, and subsequently adjusted by Diamond Offshore management, and the estimated synergies (as defined below) prepared by Diamond Offshore management and discussed with and reviewed by Noble management. None of the forecasted financial information has been prepared with a view toward public disclosure other than to certain parties involved in the transactions or toward complying with SEC guidelines, GAAP or the guidelines established by the American Institute of Certified Public Accountants for preparation or presentation of prospective financial information. The forecasted financial information was based on numerous variables and assumptions that were deemed to be reasonable as of the respective dates when such projections were finalized. However, such assumptions are inherently uncertain and difficult or impossible to predict or estimate and most of them are beyond Diamond Offshore’s or Noble’s control. In addition, the forecasted financial information (other than the estimated synergies) was prepared on the assumption that each of Diamond Offshore and Noble, as applicable, would remain a standalone company and was based on a number of other assumptions that may now be outdated. It is likely that the contribution of Diamond Offshore’s business to Noble’s consolidated results will be materially different from Diamond Offshore’s performance on a standalone basis. The forecasted financial information also reflects assumptions regarding the continuing nature of certain business decisions that are subject to change, including the matters discussed in this section titled “Risk Factors” and those other matters described in the section titled “Cautionary Note Regarding Forward-Looking Statements” beginning on page 24. Important factors that may affect actual results of Noble’s operations following the transactions, or could lead to the forecasted financial information not being achieved include, but are not limited to: changes in commodity prices; decline in the price of oil or gas, reduced demand for oil and gas products and increased regulation of drilling and production; price competition and cyclicality in the offshore drilling industry, offshore rig supply, dayrates and demand for rigs; contract duration, renewal, terminations and repricing, national oil companies and governmental clients, contract backlog, customer and geographic concentration; operational hazards and risks; and international operations and related mobilization and demobilization of rigs, operational interruptions, delays, upgrades, refurbishment and repair of rigs and any related delays and cost overruns or reduced payment of dayrates. As such, forecasted financial information may be inaccurate and should not be relied upon as an indicator of actual past or future results.

Further, any forward-looking statement speaks only as of the date on which it is made, and none of Diamond Offshore, Noble or any of their respective affiliates, officers, directors, advisors or other representatives undertakes any obligation, other than as required by applicable law, to update the forecasted financial information to reflect events or circumstances after the date those financial estimates were prepared or to reflect the occurrence of anticipated or unanticipated events or circumstances.

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The forecasted financial information is the responsibility of Diamond Offshore. Moreover, none of Diamond Offshore’s independent registered public accounting firm, Noble’s independent registered public accounting firm or any other independent accountants, have audited, compiled, examined or performed any agreed-upon procedures with respect to the forecasted financial information contained in this proxy statement/prospectus, and none has expressed any opinion or any other form of assurance on such information or its achievability. The reports of such independent registered public accounting firms incorporated by reference herein relate to the historical financial information of the entities named in those reports, and do not extend to the forecasted financial information and should not be read to do so. For more information, see the section titled “Certain Unaudited Forecasted Financial Information” beginning on page 40.

Noble’s obligation to consummate the transactions is not conditioned on the availability of financing to pay the cash portion of the merger consideration.

Noble intends to finance the cash portion of the merger consideration through a combination of cash on hand and debt financing, which may include senior unsecured bridge loans and/or one or more notes issuance. On June 10, 2024, one of Noble’s subsidiaries entered into the commitment letter with Morgan Stanley Senior Funding, Inc., pursuant to which, subject to the terms and conditions set forth therein, Morgan Stanley Senior Funding, Inc. has committed to provide the bridge facility in an aggregate principal amount of up to $600,000,000. The funding of the bridge facility provided for in the commitment letter is contingent on the satisfaction of customary conditions, including (i) the execution and delivery of definitive documentation with respect to the bridge facility in accordance with the terms set forth in the commitment letter and (ii) the consummation of the transactions in accordance with the merger agreement. There is a risk that these conditions will not be satisfied and the debt financing may not be available when required.

On or prior to the closing date, Noble expects to issue senior unsecured notes in an aggregate principal amount up to $600,000,000, which, if issued, will be used by Noble in combination with cash on hand to finance the cash portion of the merger consideration in lieu of drawing on the bridge facility. Noble’s ability to complete the notes issuance will depend on, among other factors, prevailing market conditions and other factors beyond Noble’s control. The notes issuance could have negative consequences on Noble, including, among other things, (i) requiring Noble to dedicate a larger portion of its cash flow from operations to servicing and repayment of the debt, (ii) reducing funds available for strategic initiatives and opportunities, working capital and other general corporate needs and (iii) the indenture governing such senior unsecured notes may impose certain operating and financial restrictions on Noble, including restricting Noble’s ability to incur additional debt and provide additional guarantees; pay dividends and make other restricted payments, including certain investments; create or permit certain liens; make certain asset sales; use the proceeds from the sales of assets and subsidiary stock; create or permit restrictions on the ability of our restricted subsidiaries to pay dividends or make other distributions to us; engage in certain transactions with affiliates; make certain acquisitions; enter into sale and leaseback transactions; and consolidate, merge, or transfer all or substantially all of our assets or the assets of our restricted subsidiaries.

In the event the bridge facility and the notes issuance described above are not available, there is a risk that alternative financing may not be available or completed on acceptable terms, in a timely manner or at all. Completion of the transactions is not conditioned on Noble obtaining financing for the transactions. For additional information regarding the financing of the transactions, see the section titled “The Transactions—Treatment of Diamond Offshore Indebtedness and Financing of the Transactions” beginning on page 105.

Risks Relating to Tax Matters

You should read the discussion under the section titled “Material Tax Considerations” beginning on page 111 for a more complete discussion of U.S. federal income tax and UK tax considerations relating to the mergers and the ownership and disposition of Noble ordinary shares received in the first merger.

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The mergers may be subject to Section 367(a)(1) of the Code, potentially causing U.S. Holders of Diamond Offshore common stock to recognize gain for U.S. federal income tax purposes.

The parties intend that the mergers, taken together, will qualify as a tax-free reorganization within the meaning of Section 368(a) of the Code, and that the mergers will not be subject to Section 367(a)(1) of the Code, except with respect to a five-percent transferee shareholder, if any, as defined in Treasury Regulations Section 1.367(a)-3(c)(5)(ii). Assuming, as the parties intend, that the mergers are treated as a reorganization under Section 368(a) of the Code, and that the mergers are not subject to Section 367(a)(1) of the Code, a U.S. Holder of Diamond Offshore common stock that is not a five-percent transferee shareholder generally will not recognize any realized loss but will recognize any realized gain as a result of the mergers equal to the lesser of (i) the excess, if any, of (A) the sum of the fair market value of Noble ordinary shares (including any fractional share of Noble ordinary shares deemed received and redeemed for cash, as discussed in “Material Tax Considerations—Material U.S. Federal Income Tax Considerations—U.S. federal income tax consequences of the mergers to U.S. Holders”) and the amount of cash consideration (excluding the amount of any cash in lieu of a fractional share of Noble ordinary shares) received by such U.S. Holder pursuant to the first merger over (B) such U.S. Holder’s adjusted tax basis in the Diamond Offshore common stock surrendered pursuant to the first merger and (ii) the amount of cash consideration (excluding the amount of any cash in lieu of a fractional share of Noble ordinary shares) received by such U.S. Holder pursuant to the first merger.

Notwithstanding the above, until the closing, the parties cannot definitively determine the application of Section 367(a)(1) of the Code to the mergers. In addition, no assurances can be given that the U.S. Internal Revenue Service (the “IRS”) will not assert, or that a court would not sustain, that the mergers are subject to Section 367(a)(1) of the Code.

If Section 367(a)(1) of the Code were to apply to the mergers, a U.S. Holder of Diamond Offshore common stock would recognize gain (but not loss) equal to the excess, if any, of (x) the fair market value as of the closing date of any Noble ordinary shares received in the first merger, plus cash received in the first merger, over (y) such U.S. Holder’s tax basis in the Diamond Offshore common stock surrendered in the first merger, as calculated separately for each block of Diamond Offshore common stock held by such U.S. Holder. Any gain so recognized would generally be long-term capital gain if the U.S. Holder held the Diamond Offshore common stock for more than one year at the time the mergers are completed.

For a more complete description of the U.S. federal income tax consequences of the mergers, see the section titled “Material Tax Considerations—Material U.S. Federal Income Tax Considerations” beginning on page 111.

Other Risk Factors of Noble and Diamond Offshore

Noble’s and Diamond Offshore’s businesses are and will be subject to all the risks described above. In addition, Noble and Diamond Offshore are and will continue to be subject to all the risks described in Noble’s and Diamond Offshore’s respective Annual Reports on Form 10-K for the fiscal year ended December 31, 2023, as such risks may be updated or supplemented in each company’s subsequently filed Quarterly Reports on Form 10-Q or Current Reports on Form 8-K, all of which are filed with the SEC and incorporated by reference into this proxy statement/prospectus. For the location of information incorporated by reference into this proxy statement/prospectus, see the section titled “Where You Can Find More Information” beginning on page 205.

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UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL INFORMATION OF NOBLE

On June 9, 2024, Noble entered into the merger agreement with Diamond Offshore and other indirect, wholly owned subsidiaries of Noble. The merger agreement provides that, among other things and subject to the terms and conditions therein, Diamond Offshore would become through the transactions an indirect wholly owned subsidiary of Noble. The transactions would be accounted for as a business combination pursuant to Accounting Standards Codification Topic 805, Business Combinations (“ASC 805”), where Noble would be the accounting acquirer.

The unaudited pro forma condensed combined financial statements of Noble and the accompanying footnotes (the “pro forma financial information”) reflects the impact of the contemplated transactions, including the notes issuance, and has been prepared under the following assumptions:

The pro forma financial information does not represent what the actual consolidated results of operations or the consolidated financial position of Noble would have been had the transactions occurred on the dates assumed, nor are they necessarily indicative of future consolidated results of operations or consolidated financial position. The assumptions underlying the pro forma adjustments are described in the accompanying notes to these unaudited pro forma condensed combined financial statements. Adjustments are based on information available to management during the preparation of the pro forma financial information and assumptions that management believes are reasonable and supportable. The pro forma adjustments, which are described in the accompanying notes, may be revised as additional information becomes available and is evaluated. Therefore, it is likely that the actual adjustments upon the completion of the transactions will differ from the pro forma adjustments, and it is possible the differences may be material.

The pro forma financial information should be read in conjunction with the following:

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Unaudited Pro Forma Condensed Combined Statement of Operations

Three Months Ended March 31, 2024

(in thousands, except per share amounts)

The accompanying notes are an integral part of these unaudited pro forma condensed combined financial statements.

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Unaudited Pro Forma Condensed Combined Statement of Operations

Twelve Months Ended December 31, 2023

(in thousands, except per share amounts)

The accompanying notes are an integral part of these unaudited pro forma condensed combined financial statements.

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Unaudited Pro Forma Condensed Combined Balance Sheet

As of March 31, 2024

(in thousands)

The accompanying notes are an integral part of these unaudited pro forma condensed combined financial statements.

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NOTES TO UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL INFORMATION

Note 1. Basis of Presentation

The pro forma financial information has been prepared in accordance with Article 11 of Regulation S-X as amended by the final rule, Release No. 33-10786 “Amendments to Financial Disclosures about Acquired and Disposed Businesses,” using assumptions set forth in the notes herein. Article 11 permits presentation of reasonably estimable synergies and other transaction effects that have occurred or are reasonably expected to occur (“management’s adjustments”). Noble has elected not to present management’s adjustments and will only be presenting transaction accounting adjustments in the pro forma financial information.

The historical consolidated financial statements of Noble and Diamond Offshore were prepared in accordance with accounting policies generally accepted in the United States of America and shown in U.S. dollars.

Note 2. Accounting for the Transactions

Merger Agreement

Subject to the terms and conditions set forth in the merger agreement, at the effective time:

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Purchase Price Consideration

The following table presents the calculation of preliminary purchase price consideration (in thousands, except ratios and per share price):

Preliminary purchase price consideration

The purchase price consideration calculated above and applied in the pro forma financial information is preliminary and subject to modification based on the actual number of Noble ordinary shares issued, the number of vested Diamond Offshore RSUs and Diamond Offshore PSUs, and the market price of the Noble ordinary shares at the closing of the transactions. A 10% change in the closing price of Noble common stock, as compared to the June 24, 2024 closing price of $44.99, would increase or decrease the consideration by approximately $125.6 million, assuming all other factors are held constant.

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Allocation of Purchase Price Consideration to Assets Acquired and Liabilities Assumed

The allocation of the consideration, including any related tax effects, is preliminary and pending finalization of various estimates, inputs and analyses used in the valuation assessment of the specifically identifiable tangible and intangible assets acquired and liabilities assumed. Since the pro forma financial information has been prepared based on preliminary estimates of consideration and fair values attributable to the transactions, the actual amounts eventually recorded in accordance with the acquisition method of accounting may differ materially from the information presented.

ASC 805 requires, among other things, that the assets acquired and liabilities assumed in a business combination be recognized at their fair values as of the acquisition date. Any consideration transferred or paid in a business combination in excess of the fair value of the assets acquired and liabilities assumed should be recognized as goodwill. Management’s estimate as of the date of this proxy statement/prospectus is that the fair value of the net assets and liabilities acquired equals the purchase price.

The preliminary purchase price allocation is subject to change due to several factors, including, but not limited to, the following:

The preliminary allocation of the purchase price consideration is as follows (in thousands):

Purchase Price Allocation

Note 3. Accounting Policies and Reclassification Adjustments

Upon completion of the acquisition, Noble will perform a comprehensive review of Diamond Offshore’s accounting policies. As a result of the review, Noble may identify differences between the accounting policies

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which, when conformed, could have a material impact on the financial statements of the combined company. Based on an initial analysis, management did not identify any differences that would have a material impact on the unaudited pro forma condensed combined financial information, except the presentation reclassifications further discussed below.

The following reclassifications were made to conform Diamond Offshore’s historical financial information to Noble’s presentation:

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Note 4. Transactions Accounting Adjustments

The transactions accounting adjustments below are prepared based on the purchase price assumptions presented in Note 2.

Condensed Combined Statements of Operations

(A) Amortization of off-market contracts

Reflects the amortization of off-market contract intangible assets and liabilities identified as a result of the transactions.

(B) Depreciation and amortization

Reflects the removal of historical depreciation expense and the recording of the pro forma depreciation expense based on the estimated fair value and useful lives of property and equipment upon consummation of the transactions. Drilling equipment and facilities are depreciated using the straight-line method over their estimated useful lives as of the date placed in service or date of major refurbishment. Estimated useful lives of our drilling equipment range from three to thirty years. Other property and equipment is depreciated using the straight-line method over useful lives ranging from two to forty years.

(C) Share-based compensation

Reflects the difference between Diamond Offshore’s historical share-based compensation expense and the estimated share-based compensation expense related to replacement awards issued to continuing employees as part of the transactions. The fair value of the replacement share-based awards will be recognized ratably over post-combination service period.

(D) Interest expense

Reflects the net change in interest expense related to the following activities (in thousands):

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Condensed Combined Statements of Operations Adjustments

Interest expense