SOUTHERN GAS NETWORKS PLC (the "Issuer")

(Legal Entity Identifier: 549300SPX8573VZ2SK79)

Publication of Supplementary Prospectus

The following Supplementary Prospectus has been approved by the Financial Conduct Authority and is available for viewing:

The supplementary prospectus dated 28 March 2025 (the "Supplementary Prospectus") supplements the prospectus dated 3 October 2024 (the "Prospectus") relating to the £5,000,000,000 Euro Medium Term Note Programme established by the Issuers.

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/7282C_1-2025-3-28.pdf

A copy of the Supplementary Prospectus has been submitted to the National Storage Mechanism and will shortly be available for inspection at: https://data.fca.org.uk/#/nsm/nationalstoragemechanism

For further information, please contact:

Nilesh Patel

Treasurer

St Lawrence House

Station Approach

Horley, Surrey

RH6 9HJ

[email protected]

[email protected]

DISCLAIMER - INTENDED ADDRESSEES

Please note that the information contained in the 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 Prospectus is not addressed. The Prospectus is not intended for use in the United States and is not addressed or targeted at U.S. persons and should not be relied upon by any U.S. person. Prior to relying on the information contained in the Prospectus, you must ascertain from the Prospectus whether or not you are one of the intended addressees of the information contained therein.

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