Spirent Communications PLC announces Holding(s) in Company


Crawley, UK -- (MARKET WIRE) -- March 27, 2007 --


TR-1(i):       NOTIFICATION OF MAJOR INTERESTS IN SHARES


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

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 pecify):___________________________________________    


3.  Full name of person(s) subject to the     Credit Suisse Asset 
    notification obligation (iii):            Management Limited
                                                               
                                                                 
4.  Full name of shareholder(s) (if           HSBC Global Custody 
    different from 3.)(iv):                   Nominees (UK) Limited
                                              JPM Chase Nominees Limited
                                              ROY Nominees Limited
                                              Vidacos Nominees Limited

5.  Date of the transaction (and date on      22/03/2007
    which the threshold is crossed or 
    reached if different)(v):

6.  Date on which issuer notified:            26/03/2007

7.  Threshold(s) that is/are crossed 
    or reached:                               6%

8.  Notified details:


A: Voting rights attached to shares

Class/type of shares         Situation previous to the Triggering 
transaction if possible      (vi)
using the ISIN CODE
                             Number of Shares   Number of Voting Rights 
                                                                   viii

GB0004726096                       52,187,604                52,187,604


A: Voting rights attached to shares

Class/type of shares      Resulting situation after the triggering 
transaction if possible   (vii)
using the ISIN CODE
                     Number of   Number of voting rights   % of voting
                        shares                        ix        rights
              
                        Direct   Direct x  Indirect xi    Direct  Indirect
                                                      
GB0004726096        55,687,604  55,687,604           0     6.28%       0


B: Financial Instruments

Resulting situation after the triggering transaction xii

Type of financial          Expiration date    Exercise/ Conversion 
Period/ Date               xiii               xiv
instrument                

N/A                        N/A                N/A

B: Financial Instruments

Resulting situation after the triggering transaction xii

Number of voting rights that may be        % of voting rights
acquired if the instrument is 
exercised/ converted.                      

N/A                                        N/A

Total (A+B)

Number of voting rights                            % of voting rights

55,687,604                                         6.28%


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 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:                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:                  N/A


14.  Contact name:                            Ross Keogh


15.  Contact telephone number:                020 7888 9746


C:   Additional information


Contact at Issuer:                            Michael Anscombe, 
                                              Deputy Company Secretary, 
                                              Spirent Communications plc

Telephone:                                    01293 767676


--------------------------

NOTES:
      
(i)   This form is to be sent to the issuer or underlying issuer and to
      be filed with the competent authority.

(ii)  Either the full name of the legal entity or another method for
      identifying the issuer or underlying issuer, provided it is 
      reliable and accurate.

(iii) This should be the full name of (a) the shareholder; (b) the
      person acquiring, disposing of or exercising voting rights in the 
      cases provided for in DTR5.2.1 (b) to (h);  (c) all the parties to 
      the agreement referred to in DTR5.2.1 (a), or (d) the direct or 
      indirect holder of financial instruments entitled to acquire shares 
      already issued to which voting rights are attached, as appropriate.

In relation to the transactions referred to in points DTR5.2.1 (b) to 
(h), the following list is provided as indication of the persons who 
should be mentioned:
      
-     in the circumstances foreseen in  DTR5.2.1 (b), the person that
      acquires the voting rights and is entitled to exercise them under 
      the agreement and the natural person or legal entity who is 
      transferring temporarily for consideration the voting rights;

-     in the circumstances foreseen in DTR 5.2.1 (c), the person holding
      the collateral, provided the person or entity controls the voting 
      rights and declares its intention of exercising them, and person 
      lodging the collateral under these conditions;

-     in the circumstances foreseen in DTR5.2.1(d), the person who has a
      life interest in shares if that person is entitled to exercise the 
      voting rights attached to the shares and the person who is 
      disposing of the voting rights when the life interest is created;

-     in the circumstances foreseen in DTR5.2.1 (e), the parent
      undertaking and, provided it has a notification duty at an 
      individual level under DTR 5.1, under DTR5.2.1 (a) to (d) or under 
      a combination of any of those situations, the controlled 
      undertaking;

-     in the circumstances foreseen in DTR5.2.1 (f), the deposit taker of
      the shares, if he can exercise the voting rights attached to the 
      shares deposited with him at his discretion, and the depositor of 
      the shares allowing the deposit taker to exercise the voting rights 
      at his discretion;

-     in the circumstances foreseen in DTR5.2.1 (g), the person  that
      controls the voting rights;

-     in the circumstances foreseen in DTR5.2.1 (h), the proxy holder, if
      he can exercise the voting rights at his discretion, and the 
      shareholder who has given his proxy to the proxy holder allowing 
      the latter to exercise the voting rights at his discretion.

(iv)  Applicable in the cases provided for in DTR 5.2.1 (b) to (h). This
      should be the full name of the shareholder or holder of financial 
      instruments who is the counterparty to the natural person or legal 
      entity referred to in DTR5.2.


(v)   The date of the transaction should normally be, in the case of an
      on exchange transaction, the date on which the matching of orders 
      occurs; in the case of an off exchange transaction, date of the 
      entering into an agreement.

The date on which threshold is crossed should normally be the date on 
which the cquisition, disposal or possibility to exercise voting rights 
takes effect (see DTR 5.1.1R (3)). For passive crossings, the date when 
the corporate event took effect.

These dates will usually be the same unless the transaction is subject to 
a condition beyond the control of the parties.


(vi)   Please refer to the situation disclosed in the previous
       notification, In case the situation previous to the triggering 
       transaction was below 3%, please state 'below 3%'.

vii    If the holding has fallen below the minimum threshold , the
       notifying party should not be obliged to disclose the extent of 
       the holding, only that the new holding is less than 3%.


For the case provided for in DTR5.2.1(a), there should be no disclosure of
individual holdings per party to the agreement unless a party individually
crosses or reaches an Article 9 threshold. This applies upon entering 
into, introducing changes to or terminating an agreement.

viii   Direct and indirect

ix     In case of combined holdings of shares with voting rights 
       attached ' direct holding' and voting rights 'indirect holdings', 
       please split the voting rights number and percentage into the 
       direct and indirect columns-if there is no combined holdings, 
       please leave the relevant box blank.

X      Voting rights attached to shares in respect of which the notifying
       party is a direct shareholder  (DTR 5.1)

xi     Voting rights held by the notifying party as an indirect
       shareholder (DTR 5.2.1)

xii    If the holding has fallen below the minimum threshold, the 
       notifying party should not be obliged to disclose the extent of 
       the holding, only that the new holding is below 3%.

xiii   date of maturity / expiration of the finical instrument i.e. the
       date when the right to acquire shares ends.

xiv    If the financial instrument has such a period-please specify the
       period- for example once every three months starting from the 
       (date)

xv     The notification should include the name(s) of the controlled
       undertakings through which the voting rights are held. The 
       notification should also include the amount of voting rights and 
       the percentage held by each controlled undertaking, insofar as 
       individually the controlled undertaking holds 3% or more, and 
       insofar as the notification by the parent undertaking is
       intended to cover the notification obligations of the controlled 
       undertaking.

xvi    This annex is only to be filed with the competent authority.

xvii   Whenever another person makes the notification on behalf of the
       shareholder or the natural person/legal entity  referred to in 
       DTR5.2 and DTR5.3.

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