Holding(s) in Company

Cookson Group PLC
07 September 2006


                   NOTIFICATION OF MAJOR INTERESTS IN SHARES



1. Name of company


Cookson Group plc



2. Name of shareholder having a major interest


Aviva plc and its subsidiaries



3. Please state whether notification indicates that it is in respect of holding
of the shareholder named in 2 above or in respect of a non-beneficial interest
or in the case of an individual holder if it is a holding of that person's
spouse or children under the age of 18


As in 2 above



4. Name of the registered holder(s) and, if more than one holder, the number of
shares held by each of them


Morley Fund Management Ltd:

BNY Norwich Union Nominees Limited                  2,354,549*

Chase GA Group Nominees Limited                     5,098,773*

Chase Nominees Limited                                223,302*

CUIM Nominee Limited                                2,069,950*



* denotes beneficial interest



5. Number of shares / amount of stock acquired


393,377



6. Percentage of issued class


0.20%



7. Number of shares / amount of stock disposed


n/a



8. Percentage of issued class


n/a



9. Class of security


Ordinary Shares of 10 pence each



10. Date of transaction


5 September 2006



11. Date company informed


6 September 2006



12. Total holding following this notification


9,746,574*



*  beneficial interest only



13. Total percentage holding of issued class following this notification


5.06%



14. Any additional information






15. Name of contact and telephone number for queries


Rachel Fell, Deputy Secretary, Cookson Group plc - Tel: [phone]




16. Name and signature of authorised company official responsible for making
this notification


Rachel Fell, Deputy Secretary, Cookson Group plc




Date of notification


7 September 2006



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