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 November, 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

     AVIVA plc

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

     SHAREHOLDER IN 2 ABOVE

4    Name of the registered holder(s) and, if more
     than one holder, the number of shares held by
     each of them

     -

5    Number of shares   6 Percentage of    7  Number of shares   8   Percentage
     / amount of          Issued              /amount of stock       of Issued
     stock acquired       Class               disposed               Class




     -                    -                    1,380,763              0.15%




9     Class of security                 10    Date of transaction

      ORDINARY SHARES OF 3 1/3p EACH          18 November 2002


11   Date company informed

     20 November 2002


12    Total holding following this notification

      36,641,341


13    Total percentage holding of issued class following
      this notification

      3.90%

14   Any additional information

     NOTIFICATION IN ACCORDANCE WITH S.198-202
     COMPANIES ACT 1985

15   Name of contact and telephone number for queries

     LUKE THOMAS 01293 767658



16   Name and signature of authorised company official
     responsible for making this notification


     Date of notification 21 NOVEMBER 2002         LUKE THOMAS -
                                                   DEPUTY COMPANY SECRETARY




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  21 November, 2002                   By   ____/s/ Luke Thomas____

                                                    (Signature)*