REG-Cookson Group PLC: Holding(s) in Company

TR-1: NOTIFICATION 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 the notification (please state 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): ( )

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

Aviva plc & its subsidiaries

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

Registered Holders:

BNY Norwich Union Nominees Limited 962,190*

Chase GA Group Nominees Limited 6,450,921*

Chase Nominees Limited 200,374*

CUIM Nominee Limited 464,517*

Vidacos Nominees Limited 55,902*

* denotes direct interest

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

9 July 2009

6. Date on which issuer notified:

13 July 2009

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

3% to <3% change at Direct Interest Level

8. Notified details:

A: Voting rights attached to shares

Class/type of shares if possible Situation previous to the
using the ISIN CODE Triggering transaction

Number of shares Number of voting
Rights

Ordinary Shares

GBP 1.00

GB00B3WK5475

10,729,257 10,729,257

Resulting situation after the triggering transaction

Class/type of shares if possible Number of Number of voting % of voting rights
using the ISIN CODE shares rights

Direct Direct Indirect Direct Indirect

Ordinary Shares

GBP 1.00

GB00B3WK5475

8,133,904 8,133,904 Not 2.94 Not
disclosable disclosable

B: Financial Instruments

Resulting situation after the triggering transaction

Type of Expiration Exercise/ Number of voting rights that may be % of
financial Date Conversion acquired if the instrument is voting
instrument Period/ Date exercised/ converted. rights

N/A

Total (A+B)

Number of voting % of voting
rights rights

8,133,904 2.94

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 the proxy holder:

See Section 4

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:

RACHEL FELL, DEPUTY SECRETARY, COOKSON GROUP PLC

15. Contact telephone number:

020 7822 0000

END