Publication of Supplementary Prospectus

Publication of Supplementary Prospectus

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

The Supplementary Prospectus dated 23 November 2018 (the "Supplementary Prospectus") supplementing the prospectus dated 2 August 2018 (the "Prospectus") for the National Grid plc and National Grid Electricity Transmission plc Euro 15,000,000,000 Euro Medium Term Note Programme.

The Supplementary Prospectus should be read and construed in conjunction with the Prospectus.

To view the Supplementary Prospectus, please paste the following URL into the address bar of your browser:

[http://www.rns-pdf.londonstockexchange.com/rns/3932I_1-2018-11-23.pdf

A copy of the Supplementary Prospectus 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 LiuDeputy Treasurer, Funding & InvestmentNational Grid plc1-3 StrandLondon WC2N 5EH

Tel: +44 (0) 20 7004 3367

Fax: +44 (0) 20 7004 3363

Sean KempMedia RelationsNational Grid plcWarwick House

Warwick Technology Park

Gallows Hill

Warwick

CV34 6DA

Tel: +44 (0) 7960 012356

Fax: +44 (0)192665 5633

DISCLAIMER - INTENDED ADDRESSEES

Please note that the information contained in the Supplementary Prospectus may be addressed to and/or targeted at persons who are residents of particular countries (specified in the Prospectus) 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 Supplementary Prospectus is not addressed. Prior to relying on the information contained in the Supplementary Prospectus you must ascertain from the Prospectus 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.