Costain Regulatory News (COST)

For filings with the FSA include the annex

For filings with issuer exclude the annex

TR-1: NOTIFICATION OF MAJOR INTEREST IN SHARES

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

 Costain Group PLC

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

An acquisition or disposal of voting rights

No 

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

No 

An acquisition or disposal of instruments with similar economic effect to qualifying financial instruments

No 

An event changing the breakdown of voting rights

No 

Other (please specify):

Yes 

3. Full name of person(s) subject to the notification obligation:

 Gartmore Investment Limited

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

5. Date of the transaction and date on which the threshold is crossed or reached:

 1st June 2009

6. Date on which issuer notified:

 2nd June 2009

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

5% 

8. Notified details:

A: Voting rights attached to shares

Class/type of shares

if possible using the ISIN CODE

Situation previous to the triggering transaction

Resulting situation after the triggering transaction

Number of Shares

Number of Voting Rights

Number of shares

Number of voting rights

% of voting rights

Direct

Direct

Indirect

Direct

Indirect

GB0002272184

31,148,163

31,148,163 

 26,741,507

26,741,507 

 4.22%

B: Qualifying Financial Instruments

Resulting situation after the triggering transaction

Type of financial instrument

Expiration date

Exercise/ Conversion Period

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

% of voting rights

C: Financial Instruments with similar economic effect to Qualifying Financial Instruments

Resulting situation after the triggering transaction

Type of financial instrument

Exercise price

Expiration date

Exercise/ Conversion period

Number of voting rights instrument refers to

% of voting rights

 CFD

 N/A

 N/A

 N/A.

5,407,114

Nominal

Delta

 0.853%

Total (A+B+C)

Number of voting rights

Percentage of voting rights

 32,148,621

5.073%

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

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:

 All figures are based on the Companies issued share capital of 633,696,391 as provided by Exshare

E mail contact  RDU@Gartmore.com

14. Contact name:

 RDU

15. Contact telephone number:

 0207 782 2324