Holding(s) in Company

Spirent PLC
20 January 2006

                   NOTIFICATION OF MAJOR INTERESTS IN SHARES



1. Name of listed company


SPIRENT PLC


2. Name of shareholder with a major interest


SUN LIFE ASSURANCE COMPANY OF CANADA (UK) LIMITED


3. Please state whether notification indicates that regarding the holding of the
shareholder named in 2 above; 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


ROY Nominees                                               13,021,568
ROY Nominees                                               14,244,133
ROY Nominees                                                   10,926
ROY Nominees                                                2,488,640

TOTAL                                                      29,765,267


5. Number of shares / amount of stock acquired


NOT KNOWN



6. Percentage of issued class (any treasury shares held by the listed company
should not be taken into account when calculating percentage)


NOT KNOWN


7. Number of shares / amount of stock disposed


-


8. Percentage of issued class (any treasury shares held by the listed company
should not be taken into account when calculating percentage)


-


9. Class of security


ORDINARY SHARES OF 3.3333 PENCE EACH


10. Date of transaction


NOT NOTIFIED


11. Date company informed


20 JANUARY 2006


12. Total holding following this notification


29,765,267


13. Total percentage holding of issued class following this notification (any
treasury shares held by the listed company should not be taken into account when
calculating percentage)


3.08%


14. Any additional information


15. Name of contact and telephone number for queries


MICHAEL ANSCOMBE - 01293 767672



16. Name and signature of duly authorised company official of the listed company
responsible for making this notification


MICHAEL ANSCOMBE - ASSISTANT COMPANY SECRETARY


Date of notification


20 JANUARY 2006






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