Holding(s) in Company

Spirent Communications PLC
31 January 2008

          
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             Prudential plc group of companies
     obligation:


4.   Full name of shareholder(s) (if different from 3.):             MAGIM HSBC GIS NOM(UK) SALI
                                                                    NORTRUST NOMINEE LTD A/C MHF01
                                                                    NORTRUST NOMINEE LTD A/C MHJ01
                                                                    NORTRUST NOMINEE LTD A/C MKB01
                                                                    NORTRUST NOMINEE LTD A/C MKM01
                                                                          NORTRUST NOMS LTD
                                                                     NORTRUST NOMS LTD A/C PUF01
                                                                     NORTRUST NOMS LTD A/C PUI01
                                                                     NORTRUST NOMS LTD A/C PUQ01
                                                                      NORTUST NOMS LTD A/C PUR01
                                                                    PPL UK EQUITY 350 PASSIVE FUND
                                                                      PPL UK EQUITY GROWTH FUND
                                                                    PRUCLT HSBC GIS NOM(UK) PAC AC
                                                                    PRUCLT HSBC GIS NOM(UK) PPL AC
                                                                   PRUCLT HSBC GIS NOM(UK) EQBF AC
                                                                   PRUCLT HSBC GIS NOM(UK) MNBF AC
                                                                   PRUCLT HSBC GIS NOM(UK) PENE AC

5.   Date of the transaction (and date on which the threshold is             29 January 2008
     crossed or reached if different):

6.   Date on which issuer notified:                                          31 January 2008

7.   Threshold(s) that is/are crossed or reached:                                  11%

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         % of voting rights
(if possible using     Shares    Voting Rights      shares         rights
the ISIN CODE)                                      Direct         Direct    Indirect   Direct   Indirect
GB0004726096        85,924,004    85,924,004      85,384,504     85,384,504             10.95%

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
85,384,504                                         10.95%



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       N/A
     rights:

13. Additional information:                Prudential plc (parent Company) has dropped below a 11%
                                           notifiable interest triggering this notification. Please
                                           note M&G Limited and M&G Group Limited have also fallen
                                           below 11%.

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

15. Contact telephone number:              020 7548 2293

Additional information


Contact at Issuer: Michael Anscombe, Company Secretary, Spirent Communications plc
Telephone: [phone]



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