Holding(s) in Company

Spirent Communications PLC
13 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

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): A purchase of shares plus an update to the total        
                        voting rights figure                                    X

3. Full name of person(s) subject to the notification             Prudential plc group of companies
obligation:

4. Full name of shareholder(s) (if different from 3.):                  See attached schedule

5. Date of the transaction (and date on which the threshold is             09 November 2007
crossed or reached if different):

6. Date on which issuer notified:                                          13 November 2007

7. Threshold(s) that is/are crossed or reached:                                  10%


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
(if possible using     Shares    Voting Rights      shares                 ix                 rights
the ISIN CODE)                                      Direct          Direct     Indirect   Direct  Indirect

GB0004726096        81,342,370   81,342,370     82,892,370      82,892,370               10.01%


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

        N/A          N/A                        N/A            N/A                        N/A


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

82,892,370                                         10.01%


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

Prudential plc (parent Company)

M&G Group Limited (wholly owned subsidiary of Prudential plc)

M&G Limited (wholly owned subsidiary of M&G Group Limited)

M&G Investment Management Limited (wholly owned subsidiary of M&G Limited)

The Prudential Assurance Company Limited (wholly owned subsidiary of Prudential plc)


Proxy Voting:
10. Name of the proxy holder:                                      N/A

11. Number of voting rights proxy holder will cease to hold:       N/A

12. Date on which proxy holder will cease to hold voting rights:   N/A


13. Additional information:

14. Contact name:                            Emma Thompson
                                             M&G Investment Management Limited

15. Contact telephone number:                020 7548 2293


Additional information
Contact at Issuer: Michelle Balch, Assistant Company Secretary, 
Spirent Communications plc

Telephone: [phone]




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