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 October, 2003

                                 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

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

COMPANY NAMED IN BOX 2 ABOVE AND ITS 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 MANHATTAN BANK LONDON (FISL)                                       146,079
HSBC (FPM)                                                               232,800
CHASE NOMINEES LTD (FPM)                                               2,761,396
NORTHERN TRUST (FPM)                                                     807,100
CHASE MANHATTAN BANK LONDON (FIL)                                        802,258
BANK OF NEW YORK BRUSSELS (FIL)                                          322,400
NORTHERN TRUST (FIL)                                                   1,107,700
CHASE NOMINEES LTD (FIL)                                               4,063,613
BANK OF NEW YORK LONDON (FIL)                                            648,066
NORTRUST NOMINEES LTD (FIL)                                            1,236,300
STATE STREET BANK & TRUST (FIL)                                          117,000
HSBC CLIENT HOLDINGS NOMINEE (UK) LIMITED (FIL)                       21,403,643

FISL = Fidelity Investment Services Limited
FPM = Fidelity Pension Management
FIL = Fidelity International Limited

5. Number of shares / amount of stock acquired

-

6. Percentage of issued class

-

7. Number of shares / amount of stock disposed

10,200,057

8. Percentage of issued class

1.08%

9. Class of security

ORDINARY SHARES OF 3.3333 PENCE EACH

10. Date of transaction

NOT NOTIFIED

11. Date company informed

24 OCTOBER 2003

12. Total holding following this notification

33,648,355

13. Total percentage holding of issued class following this notification

3.57%

14. Any additional information

-

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

24 OCTOBER 2003



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.


END


                                   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 24 October, 2003                          By   ____/s/ Luke Thomas____

                                                    (Signature)*