National Grid PLC — Capital/Financing Update 2020

Sep 9, 2020

National Grid plc

(incorporated with limited liability in England and Wales on 11 July 2000 under registered number 4031152)

National Grid Electricity Transmission plc

(incorporated with limited liability in England and Wales on 1 April 1989 under registered number 2366977)

Euro 15,000,000,000 Euro Medium Term Note Programme

This supplement (the "Supplement") to the prospectus dated 7 August 2020 (the "Prospectus"), which comprises a base prospectus for each of National Grid plc ("National Grid") and National Grid Electricity Transmission plc (together, the "Issuers"), constitutes a supplementary prospectus for the purposes of the Prospectus Regulation and supplementary listing particulars for the purposes of Section 81 of FSMA. This Supplement is prepared in connection with the Euro 15,000,000,000 Euro Medium Term Note Programme established by the Issuers. Terms defined in the Prospectus have the same meaning when used in this Supplement.

This Supplement is supplemental to, and should be read in conjunction with, the Prospectus and any other supplements to the Prospectus issued by the Issuers.

Each of the Issuers accepts responsibility for the information contained in this Supplement. To the best of the knowledge of each Issuer the information contained in this Supplement is in accordance with the facts and this Supplement makes no omission likely to affect the import of such information.

To the extent that there is any inconsistency between (a) any statement in this Supplement or any statement incorporated by reference into the Prospectus by this Supplement and (b) any other statement in, or incorporated by reference in, the Prospectus, the statements in this Supplement will prevail.

The Prospectus, this Supplement and the documents incorporated by reference in the Prospectus can be viewed on the website of the Regulatory News Service operated by the London Stock Exchange plc at www.londonstockexchange.com/exchange/news/market-news/market-news-home.html. If documents which are incorporated by reference themselves incorporate any information or other documents therein, such information or other documents will not form part of this Supplement for the purposes of the Prospectus Regulation and the Listing Rules except where such information or other documents are stated within this Supplement as being specifically incorporated by reference into this Supplement.

Purpose of this Supplement

The purpose of this Supplement is to incorporate by reference National Grid's announcement relating to its consultation response to Ofgem's RIIO-2 draft determinations.

Incorporation by Reference

On 7 September 2020, National Grid published a press release (the "Consultation Response Press Release") relating to its consultation response to Ofgem's RIIO-2 draft determinations. A copy of the Consultation Response Press Release has been filed with the Financial Conduct Authority and, by virtue of this Supplement, shall be deemed to be incorporated in, and form part of, the Prospectus.

General Information

Copies of all documents incorporated by reference in the Prospectus will be available on the website of National Grid, as set out in the Prospectus.

Save as disclosed in this Supplement, no significant new factor, material mistake or material inaccuracy relating to information included in the Prospectus has arisen or been noted, as the case may be, in relation to either of the Issuers since the publication of the Prospectus.