UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 6-K REPORT OF FOREIGN PRIVATE ISSUER PURSUANT TO RULE 13a-16 OR 15d-16 UNDER THE SECURITIES EXCHANGE ACT OF 1934 For the month of December, 2002 SPIRENT plc _____________________________________________________________________ (Translation of registrant's name into English) Spirent House, Crawley Business Quarter, Fleming Way, Crawley, West Sussex RH10 9QL, UK. _____________________________________________________________________ (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- ________ London Stock Exchange NOTIFICATION OF MAJOR INTERESTS IN SHARES All relevant boxes should be completed in block capital letters 1 Name of company SPIRENT plc 2 Name of shareholder having a major interest FMR Corp. and Fidelity International Limited 3 Please state whether notification indicates that it is in Respect of holding of the shareholder named in 2 above or In respect of a non-beneficial interest or in the case of an individual holder if it is a holding of that person's spouse or children under the age of 18 Companies named in box 2 above and their direct and indirect subsidiaries, being non-beneficial holders. 4 Name of the registered holder(s) and, if more than one holder, the number of shares held by each of them Chase Nominees Ltd (FMRCO) 7,011,700 State Street Nominees Ltd (FMRCO) 1,326,900 State Street Bank & Trust (FMTC) 2,184,900 Chase Manhattan Bank London (FISL) 12,462,979 HSBC (FPM) 619,700 Chase Nominees Ltd (FPM) 7,032,896 Northern Trust (FPM) 2,040,200 Chase Manhattan Bank London (FIL) 1,342,648 Bank of New York Brussels (FIL) 805,100 Northern Trust (FIL) 3,044,100 Chase Nominees Ltd (FIL) 9,979,540 Bank of New York London (FIL) 5,006,000 Nortrust Nominees Ltd (FIL) 3,107,200 State Street Bank & Trust (FIL) 296,400 TOTAL 56,260,263 FMRCO - Fidelity Management & Research Company FMTC - Fidelity Management Trust Company FISL - Fidelity Investment Services Ltd FPM - Fidelity Pension Management FIL - Fidelity International Ltd 5 Number of shares/amount of stock acquired 10,647,000 6 Percentage of Issued Class 1.13 % 7 Number of shares/amount of stock disposed N/a 8 Percentage of Issued Class N/a 9 Class of security ORDINARY SHARES OF 3 1/3p EACH 10 Date of transaction Not notified 11 Date company informed 30 December 2002 12 Total holding following this notification 56,260,263 13 Total percentage holding of issued class following this notification 5.99% 14 Any additional information 15 Name of contact and telephone number for queries Michael Anscombe - 01293 767672 16 Name and signature of authorised company official responsible for making this notification Paul Eardley, Company Secretary, Spirent plc Date of notification 30 December 2002 London Stock Exchange, Company Announcements Office, Old Broad Street, London EC2N 1HP Facsimile: 0207 588 6057, 0207 334 8964/8965/8966 (PLEASE DO NOT POST) Enquries: Continuing Obligations: Telephone: 0207 797 3850/1639/1972/3150 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. ______LUKE THOMAS______ (Registrant) Date___30 December 2002____ By ____/s/ Luke Thomas____ (Signature)*