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 January, 2004

                                   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- ________




                                  SCHEDULE 10

                   NOTIFICATION OF MAJOR INTERESTS IN SHARES



1. Name of company

SPIRENT PLC


2. Name of shareholder having a major interest

PRUDENTIAL 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 NAMED 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

NOT KNOWN


5. Number of shares / amount of stock acquired

N/A


6. Percentage of issued class

N/A


7. Number of shares / amount of stock disposed

NOT KNOWN


8. Percentage of issued class

NOT KNOWN


9. Class of security

ORDINARY SHARES OF 3.3333 PENCE EACH


10. Date of transaction

NOT KNOWN


11. Date company informed

21 JANUARY 2004


12. Total holding following this notification

NOT KNOWN


13. Total percentage holding of issued class following this notification

NOT KNOWN


14. Any additional information

IN ACCORDANCE WITH s198-202 COMPANIES ACT 1985 (AS AMENDED) SPIRENT PLC HAS
RECEIVED NOTIFICATION FROM PRUDENTIAL PLC THAT THEY NO LONGER HAVE A NOTIFIABLE
INTEREST IN THE ISSUED SHARE CAPITAL OF OUR COMPANY


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

LUKE THOMAS - DEPUTY COMPANY SECRETARY


Date of notification

22 JANUARY 2004


The FSA does not give any express or implied warranty as to the accuracy of this
document or material and does not accept any liability for error or omission.
The FSA is not liable for any damages (including, without limitation, damages
for loss of business or loss of profits) arising in contract, tort or otherwise
from the use of or inability to use this document, or any material contained in
it, or from any action or decision taken as a result of using this document or
any such material.




                                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: 22 January, 2004                      By ____/s/ Luke Thomas____

                                                   Deputy Secretary