Holding(s) in Company

Spirent Communications PLC
23 November 2007


TR-1:  NOTIFICATION OF MAJOR INTERESTS IN SHARES 

1. Identity of the issuer or the underlying issuer of existing           Spirent Communications plc
shares to which voting rights are attached:

2. Reason for the notification     (please tick the appropriate box or boxes)

An acquisition or disposal of voting rights                                                         X

An acquisition or disposal of financial instruments which may result in the acquisition of
shares already issued to which voting rights are attached

An event changing the breakdown of voting rights

Other (please specify):___________________________________________

3. Full name of person(s) subject to the notification          Sun Life Assurance Company of Canada (UK) Ltd
obligation:

4. Full name of shareholder(s) (if different from 3.):         ROY Nominees Limited

5. Date of the transaction (and date on which the threshold is 20-11-2007
crossed or reached if different):

6. Date on which issuer notified:                              23-11-2007

7. Threshold(s) that is/are crossed or reached:                3%

8. Notified details:




A: Voting rights attached to shares
Class/type of       Situation previous to the Resulting situation after the triggering transaction
shares              Triggering transaction
                    Number of    Number of    Number of     Number of voting rights % of voting rights
 if possible using  Shares       Voting       shares
the ISIN CODE                    Rights       Direct        Direct       Indirect   Direct    Indirect


GB0004726096        29,803,233   29,803,233   35,833,473    35,833,473              4.36%


B: Financial Instruments
Resulting situation after the triggering transaction xii
Type of financial    Expiration date Exercise/ Conversion      Number of voting rights    % of voting
instrument           xiii            Period/ Date xiv          that may be acquired if    rights
                                                               the instrument is
                                                               exercised/ converted.





Total (A+B)
Number of voting rights                            % of voting rights


35,833,473                                         4.36%












9. Chain of controlled undertakings through which the voting rights and/or the financial instruments are effectively
held, if applicable xv:

Credit Suisse Asset Management Ltd is making this disclosure on behalf of Sun Life Assurance Company of Canada (UK) Ltd
to whom we act as discretionary investment manager.

Credit Suisse Asset Management Limited is a segregated business unit within Credit Suisse Group (CSG) with an
independent management structure and exercises its voting rights independently from other parts of CSG.


Proxy Voting:
10. Name of the proxy holder:
11. Number of voting rights proxy holder will cease to hold:
12. Date on which proxy holder will cease to hold voting rights:


13. Additional information:
14. Contact name:                            Rebecca Suckling
15. Contact telephone number:                020 7883 9645




C:        Additional information
Contact at Issuer: Michael Anscombe, Company Secretary, Spirent Communications plc

Telephone: [phone]






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