Transaction in Own Shares

National Grid PLC
22 March 2007


National Grid plc announces that on 21 March 2007 it purchased for cancellation
500,000 of its ordinary shares at a price of 782.7319 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 2,701,728,562.
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