Holding(s) in Company

TR-1: Notifications of Major Interests in Shares

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

Cookson Group plc

2. Reason for notification (yes/no)

An acquisition or disposal of voting rights

Yes

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): On market transfer between indirect and direct funds

Yes

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

Aviva plc & its subsidiaries

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

Registered Holder:

BNY Norwich Union Nominees Limited 5,191,939*

Chase GA Group Nominees Limited

15,949,346*

Chase Nominees Limited

646,077*

CUIM Nominee Limited

3,846,345*

*denotes direct interest

Chase Nominees Limited

1,497,243

Vidacos Nominees Limited

65,215

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

25 November 2008

6. Date on which issuer notified:

27 November 2008

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

11% to 12% Change at Direct Interest Level

8: Notified Details

A: Voting rights attached to shares

Class/type of shares

If possible use 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

Percentage of voting rights

Direct

Indirect

Direct

Indirect

Ordinary Shares

GB00B07V4P80

Direct

25,017,000

Indirect

1,333,681

Direct

25,017,000

Indirect

1,333,681

25,633,707

25,633,707

1,562,458

12.06%

0.73%

B: Financial Instruments

Resulting situation after the triggering transaction

Type of financial instrument

Expiration date

Exercise/ conversion period/date 

No. of voting rights that may be acquired (if the instrument exercised/converted)

Percentage of voting rights

N/A

Total (A+B)

Number of voting rights

Percentage of voting rights

27,222,065

12.79%

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

The voting rights are managed and controlled by Aviva Investors Global Services Limited, with the following chain of controlled undertakings:-

Aviva Investors Global Services Limited:

Aviva plc (Parent Company)

Aviva Group Holdings Limited (wholly owned subsidiary of Aviva plc)

Aviva Investors Holdings Limited (wholly owned subsidiary of Aviva Group Holdings Limited)

Aviva Investors Global Services Limited (wholly owned subsidiary of Aviva Investors Holdings Limited)

Proxy Voting:

10. Name of proxy holder:

See Section 4

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:

Rachel Fell, Deputy Secretary Cookson Group plc

15. Contact telephone number:

Tel: + 44 (0)20 7822 0062