Transaction in Own Shares

National Grid PLC
21 March 2007

National Grid plc announces that on 20 March 2007 it purchased for cancellation
500,000 of its ordinary shares at a price of 769.2049 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 2,702,228,562.
--------------------------------------------------------------------------------


                      This information is provided by RNS
            The company news service from the London Stock Exchange