Holding(s) in Company

Spirent Communications PLC
20 September 2006

                   NOTIFICATION OF MAJOR INTERESTS IN SHARES

1. Name of listed company

SPIRENT COMMUNICATIONS PLC

2. Name of shareholder with a major interest

SHERBORNE INVESTORS GP, LLC

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

AS IN 2 ABOVE - SEE ADDITIONAL INFORMATION BELOW

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

SEE ADDITIONAL INFORMATION BELOW

5. Number of shares / amount of stock acquired

NOT DISCLOSED

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

N/A

7. Number of shares / amount of stock disposed

N/A

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

N/A

9. Class of security

ORDINARY SHARES OF 3 & 1/3 PENCE EACH

10. Date of transaction

NOT KNOWN

11. Date company informed


20 SEPTEMBER 2006

12. Total holding following this notification

130,250,000 ORDINARY SHARES

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)

14.31%

14. Any additional information

THE FOLLOWING ARE ALL NAMED AS INTERESTED PARTIES IN THE NOTIFICATION RECEIVED 
BY THE COMPANY:

SHERBORNE INVESTORS GP, LLC
SHERBORNE INVESTORS CO., LP
EDWARD BRAMSON (THE MANAGING MEMBER OF SHERBORNE INVESTORS GP, LLC)
CRAIG MCKIBBEN AND GERARD EASTMAN (AS MEMBERS OF SHERBORNE INVESTORS GP, LLC

THE HOLDERS OF THE SHARES AS REGISTERED ON THE COMPANY'S REGISTER OF MEMBERS ARE
NOT KNOWN.

THE NOTIFICATION ALSO DISCLOSES (IN ACCORDANCE WITH THE COMPANIES ACT 1985) THAT
THE FOLLOWING THREE ENTITIES HOLD SPIRENT COMMUNICATIONS PLC ORDINARY SHARES AS
DETAILED BELOW - THESE PERCENTAGE HOLDINGS ARE INCLUDED IN THE TOTAL 14.31%
DISCLOSED ABOVE (NOT IN ADDITION TO IT):

HAYDEN INVESTORS PARTNERS, LLC : 5.02% OF ISSUED SHARE CAPITAL
HAYDEN INVESTORS PARTNERS II, LLC: 4.49% OF ISSUED SHARE CAPITAL
HANOVER STRATEGIC FUND A, LLC: 3.26% OF ISSUED SHARE CAPITAL

15. Name of contact and telephone number for queries

MICHAEL ANSCOMBE - 01293 767676

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

MICHAEL ANSCOMBE
DEPUTY COMPANY SECRETARY

Date of notification

20 SEPTEMBER 2006


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