Publication of a Prospectus

Publication of Supplementary Prospectus

The following supplementary prospectus has been approved by the UK Listing Authority and is available for viewing:

Supplement dated 13 January 2017 (the "Supplement") to the Prospectus dated 27 September 2016 (the "Prospectus") for the National Grid plc and National Grid Electricity Transmission plc Euro 15,000,000,000 Euro Medium Term Note Programme

To view the full document, please paste the following URL into the address bar of your browser:

http://www.rns-pdf.londonstockexchange.com/rns/1778U_-2017-1-13.pdf

A copy of the Supplement has been submitted to the National Storage Mechanism and will shortly be available for inspection at http://www.morningstar.co.uk/uk/

For further information, please contact:

Kwok LiuGlobal Capital MarketsNational Grid plc1-3 StrandLondon WC2N 5EH

Tel: +44 20 7004 3367Fax: +44 20 7004 3363

Gemma StokesMedia RelationsNational Grid plcWarwick House

Warwick Technology Park

Gallows Hill

Warwick

CV34 6DA

Tel: +44 1926 655272Mob: +44 7974 198 333

DISCLAIMER - INTENDED ADDRESSEES

Please note that the information contained in the Prospectus as supplemented by the Supplement may be addressed to and/or targeted at persons who are residents of particular countries (specified in the Prospectus as supplemented by the Supplement) only and is not intended for use and should not be relied upon by any person outside these countries and/or to whom the offer contained in the Prospectus as supplemented by the Supplement is not addressed. Prior to relying on the information contained in the Prospectus as supplemented by the Supplement you must ascertain from the Prospectus as supplemented by the Supplement whether or not you are part of the intended addressees of the information contained therein.

Your right to access this service is conditional upon complying with the above requirement.