Transaction in Own Shares

National Grid PLC
07 December 2007

National Grid plc - Transaction in Own Shares

7 December 2007

National Grid plc announces that on 6 December 2007 it purchased 466,776 of its
ordinary shares at a price of 825.5631 pence per share from Morgan Stanley
Securities Limited. The purchased shares will be held as Treasury shares.

Following the purchase of these shares, the number of ordinary shares with
voting rights in issue (excluding Treasury shares) will be 2,556,738,147 and the
number of ordinary shares in Treasury will be 25,175,369.

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