RNS Number:0857Q
Marconi Corporation PLC
23 September 2003


Marconi received the following notification today:

                                       Wanger Asset Management, L.P.
                                       229 West Monroe, Suite 3000
                                       Chicago, Illinois 60606

                                       September 11, 2003

Marconi Corp PLC
Attention: Company Secretary
Regents Place
338 Euston Road
London, NW1 3BT

Ladies and Gentlemen:

We hereby notify you in fulfilment of the obligation of disclosure imposed by
the provisions of Sections 198 to 202 of the Companies Act (1985) (the "Act"),
that:

(a)  Liberty Wanger Asset Management, L.P, is interested for the purposes of the 
     Act in 6,489,000 ordinary shares each comprised in the relevant share 
     capital, as defined in Section 198(2) of the Act, of Marconi Corp PLC 
     (the "Relevant Shares");

(b)  The registered holders of the Relevant Shares are

     Wanger Advisors Trust Foreign Forty Fund - State Street Nominees Ltd  
       112,500 shares
     Liberty Acorn International Fund - State Street Nominees Ltd 
       4,837,500 shares
     Liberty Acorn Foreign Forty Fund - State Street Nominees Ltd 243,000 shares
     AXP Partners International Aggressive Growth Fund - Bank of New York 
      223,560 shares
     Wanger European Small Cap Fund - State Street Nominees Ltd 1,072,440 shares

(c)  Liberty Wanger Asset Management, L.P. is interested in the Relevant Shares 
     by virtue of section 208(4)(b) of the Act; and

(d)  This notification is given on behalf of Liberty Wanger Asset Management, 
     L.P. and its registered address at 227 W. Monroe Street, 30th Floor,
     Chicago, Illinois 60606.


Yours faithfully

Liberty Wanger Asset Management, L.P.
By WAM Acquisition GP, its general partner


Bruce H Lauer
Senior Vice President and Secretary



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