SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 6-K Report of Foreign Issuer Pursuant to Rule 13a-16 or 15d-16 of the Securities Exchange Act of 1934 For the Month of May 9, 2003 Commission file number: 0-30924 MARCONI PLC (Exact name of Registrant as specified in its Charter) 4th Floor Regents Place 338 Euston Road London NW1 3BT (Address of principal executive offices) (Indicate by check mark whether the registrant files or will file annual reports under cover Form 20-F or Form 40-F.) Form 20-F X Form 40-F (Indicate by check mark whether the registrant by furnishing the information contained in this Form is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934.) Yes No X CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS In order to utilize the "Safe Harbor" provisions of the United States Private Securities Litigation Reform Act of 1995 (the "Reform Act"), Marconi plc ( the "Company") is providing the following cautionary statement. Except for historical information contained herein, statements contained in this Report on Form 6-K may constitute "forward-looking statements" within the meaning of the Reform Act. The words "believe", "anticipate", "expect", "intend", "estimate", "plan", "assume", "positioned", "will", "may", "risk" and other similar expressions which are predictions of or indicate future events and future trends which do not relate to historical matters identify forward-looking statements. Reliance should not be placed on such statements because they involve known and unknown risks, uncertainties and other factors which are in some cases beyond the control of the Company, together with its subsidiaries (the "Group"), and may cause the actual results, performance or achievements of the Group to differ materially from anticipated future results, performance or achievements expressed or implied by such forward-looking statements (and from past results, performance or achievement). Certain factors that may cause such differences include but are not limited to the following: (1) any major disruption in production at our key facilities; (2) changes in the environmental, tax and other laws and regulations, which, among other things, could cause us to incur substantial additional capital expenditures and operation and maintenance costs; and (3) adverse changes in the markets for our products, including as a result of increased competition in the highly competitive international markets for such products. These and other risks, uncertainties and factors are discussed in the Company's Registration Statement on Form F-1 and other filings with the Securities and Exchange Commission, including this Form 6-K. Shareholders and prospective investors are cautioned not to place undue reliance on these forward-looking statements which speak only as to the Company's judgment as of the date hereof. Any such forward-looking statements are not intended to give any assurance as to future results. The Company undertakes no obligation to publicly update or revise any of these forward-looking statements, whether to reflect new information or future events or circumstances or otherwise. Marconi plc Amendment to Historic Sales Information contained in Trading Update London - 9 May 2003 - Marconi (MONI) today provided a correction to Appendix 2 of its Trading Update dated 7 May 2003 in relation to the historic quarterly breakdown of sales by product area for the year ended 31 March 2002. The table below sets forth the corrected information. Core Sales by Product Area for the year ended 31 March 2002 in GBP million FY02 Q1 Q2 Q3 Q4 Optical Networks 146 211 189 191 Broadband Routing and Switching (BBRS) 52 61 40 56 European Access 78 111 85 87 North American Access 34 31 24 32 Outside Plant & Power (OPP) 91 65 48 43 Other Network Equipment 25 38 21 45 Network Equipment 426 517 407 454 Installation, Commissioning & Maintenance (IC&M) 126 145 122 135 Value-Added Services (VAS) 98 136 103 104 Network Services 224 281 225 239 Core 650 798 632 693 Ends Notes to Editors About Marconi plc Marconi plc is a global telecommunications equipment and solutions company. The company's core business is the provision of innovative and reliable optical networks, broadband routing and switching and broadband access technologies and services. The company's customer base includes many of the world's largest telecommunications operators. The company is listed on the London Stock Exchange under the symbol MONI. Additional information about Marconi can be found at www.marconi.com. Copyright (c) 2003 Marconi plc. All rights reserved. All brands or product names are trademarks of their respective holders. Contacts Name: David Beck / Joe Kelly Heather Green Title: Public Relations Investor Relations Phone: +44 (0) 207 306 1771 +44 (0) 207 306 1735 +44 (0) 207 306 1490 joe.kelly@marconi.com heather.green@marconi.com SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized. MARCONI PLC By: ____M Skelly____ Name: M Skelly Title: Company Secretary Date: 9 May 2003