Transaction in Own Shares

National Grid PLC
23 March 2007

National Grid plc announces that on 22 March 2007 it purchased for cancellation
700,000 of its ordinary shares at a price of 785.2829 pence per share.

Following the purchase and upon the cancellation of these shares, the number of
ordinary shares with voting rights in issue will be 2,701,028,562.



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