FORM 6-K SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Report of Foreign Private Issuer Pursuant to Rule 13a-16 or 15d-16 of the Securities Exchange Act of 1934 24 March 2005 O2 plc Wellington Street Slough, Berkshire SL1 1YP, England (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... If "Yes" is marked, indicate below the file number assigned to the registrant in connection with Rule 12g3-2(b): 82 ________ Enclosure: Copy of announcement regarding 'Holding(s) in Company' sent to the London Stock Exchange on 24 March 2005 Detailed below is the content of a letter received from Fidelity Investments on 24 March 2005. O2 Contact: Emma Ridgewell Secretarial Services Assistant O2 plc t: +44 (0)1753 628227 O2 plc Wellington Street Slough Berkshire SL1 1YP United Kingdom ATTN: Company Secretary FAX: 01753-628-150 23 March 2005 Dear Sirs, Enclosed are closing amended notifications of disclosable interests under the U.K. Companies Act 1985. Please note that while this information details the disclosable interests of more than one entity, the enclosed disclosure constitutes separate notifications of interest which have been combined solely for purposes of clarity and efficiency. It is not intended to indicate that any of these entities act as a group or in concert with respect to these interests. These disclosures are made in the interest of conformity with the Companies Act. The Interest detailed herein were acquired solely for investment purposes. For disclosure purposes, holdings should be represented as FMR Corp. and its direct and indirect subsidiaries, and Fidelity International Limited (FIL) and its direct and indirect subsidiaries, both being non-beneficial holders. Please be advised that no further notifications will be processed unless a discolsable interest is obtained. If you have any questions please contact Subha Ravindran on 01737 837092 or by FAX on 01737 837450. Yours faithfully Subha Ravindran Regulatory Reporting Analyst Closing Amendment # NOTIFICATIONS UNDER SECTIONS 198 TO 202 - - U.K. COMPANIES ACT 1. Company in which shares are held: O2 plc 2. Notifiable Interest: Ordinary Shares (A) FMR Corp. 82 Devonshire Street Boston, MA 02109 Parent holding company of Fidelity Management & Research Company, (FMRCO), investment manager for US mutual funds and Fidelity Management Trust Company (FMTC), a US state chartered bank which acts as a trustee or investment manager of various pension and trust accounts. (See Schedule A for listing of Registered Shareholders and their holdings). (B) Fidelity International Limited (FIL) P.O. Box HM 670 Hamilton HMCX, Bermuda Parent holding company for various direct and indirect subsidiaries, including Fidelity Investment Services Ltd. (FISL) and Fidelity Pension Management (FPM), investment managers for various non-US investment companies and institutional clients. (See Schedule A for listing of Registered Shareholders and their holdings.) 3. The notifiable interests also comprise the notifiable interest of: Mr. Edward C. Johnson 3d 82 Devonshire Street Boston, MA 02109 A principal shareholder of FMR Corp. and Fidelity International Limited. 4. The notifiable interests include interest held on behalf of authorized unit trust schemes in the U.K., notwithstanding the exemption from reporting pursuant to Section 209 (1)(h) of the Companies Act 1985. 5. These notifications of disclosable interests constitute separate notifications of interest in the shares and are combined solely for the purposes of clarity and efficiency. Nothing herein should be taken to indicate that FMR Corp. and its direct and indirect subsidiaries, Fidelity International Limited and its direct and indirect subsidiaries or Mr. Edward C. Johnson 3d act as a group or in concert in respect of the disclosed interests, or that they are required to submit these notifications on a joint basis. 6. The disclosable interests arise under section 208 (4) (b) of the Act, namely where a person, not being the registered holder, is entitled to exercise a right conferred by the holding of the shares or to control the exercise of such rights, or under section 203 of the Act respectively. 7. In as much as there is no discolsable interest of 3% or greater of the share capital, FMR Corp. and its direct and indirect subsidiaries, and Fidelity International Limited and its direct and indirect subsidiaries have no further reporting obligation under Section 198 to 202 of the UK Companies Act. This statement speaks as of its date, and no inference should be drawn that no change has occurred in the facts set forth herein after the date hereof. By ____________________________ Rani Jandu Regulatory Reporting Manager, FIL - Investment Compliance Duly authorized under Powers of Attorney dated August 25, 2004 by Eric D. Roiter by and on behalf of FMR Corp. and its direct and indirect subsidiaries, and Fidelity International Limited and its direct and indirect subsidiaries. Schedule 'A' Nominee/Registered Name Management Company Shares Held State Street Hong Kong FIA(K)L 46,800 State Street Bank and TR Co FICL 99,900 Bank of New York Europe London FII 8,582,020 JP Morgan, Bournemouth FII 1,856,435 Bank of New York Brussels FIL 506,900 Brown Brothers Harriman Ltd. LUX FIL 92,936,073 JP Morgan, Bournemouth FIL 2,722,300 Morgan Stanley London FIL 59,394 National Australia Bank Melbourne FIL 1,171,500 Northern Trust London FIL 999,970 State Street Bank and Trust Co London FIL 778,580 JP Morgan, Bournemouth FISL 72,095,753 Brown Brothers Harriman and Co FMRCO 38,800 Northern Trust London FMRCO 403,600 Bank of New York FMTC 858,000 Brown Brothers Harriman and Co FMTC 1,757,900 JPMorgan Chase Bank FMTC 586,200 Northern Trust Co FMTC 836,500 State Street Bank and Trust Co FMTC 2,052,360 Bank of New York Brussels FPM 12,494,598 Bank of New York Europe London FPM 438,900 Chase Manhattan London FPM 40,100 Chase Manhattan Bank AG Frankfurt FPM 289,600 Citibank London FPM 714,700 Clydesdale Bank plc FPM 676,098 Dexia Privatbank FPM 33,200 JP Morgan, Bournemouth FPM 19,256,892 JP Morgan Chase Bank FPM 164,400 Mellon Bank FPM 2,482,018 Nordea Bank AB FPM 91,700 Northern Trust London FPM 19,667,025 State Street Bank and Trust Co London FPM 3,285,884 Total Ordinary Shares 248,024,100 Current ownership percentage 2.85% Shares in issue 8,703,660,323 Change in holdings since last filing (93,932,506) ordinary shares SIGNATURE 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. O2 plc Date: 24 March 2005 By:___/s/ Robert Harwood___ ROBERT HARWOOD Assistant Secretary O2 plc