Transaction in Own Shares

National Grid PLC
17 March 2008


17 March 2008


National Grid plc

Transaction in own shares: Extension of Prohibited Period Share Repurchase
Programme

National Grid plc ('National Grid') announces that it has entered into further
irrevocable, non-discretionary arrangements to purchase shares on its own behalf
for cancellation or holding in Treasury during any prohibited period which it
enters into until further notice.

Any acquisitions within a prohibited period will be effected within certain
pre-set parameters, and in accordance with both National Grid's general
authority to repurchase shares and Chapter 12 of the Listing Rules which
requires that the maximum price paid be limited to no more than 105 per cent of
the average middle market closing price of National Grid's shares for the 5
dealing days preceding the date of purchase.


Further enquiries:

Richard Smith - Investor Relations    [phone]    [phone]

David Forward - Assistant Secretary   [phone]


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