SANTANDER UK PLC

Prospectus • Sep 2, 2025

SUPPLEMENT DATED 29 AUGUST 2025 TO THE PROSPECTUS RELATING TO THE €35 BILLION GLOBAL COVERED BOND PROGRAMME OF:

SANTANDER UK PLC

(INCORPORATED IN ENGLAND WITH LIMITED LIABILITY, REGISTERED NUMBER 2294747)

This supplement (the "Supplement", which definition shall also include all information incorporated by reference herein) is supplemental to, forms part of and must be read in conjunction with, the base prospectus dated 21 March 2025, as supplemented on 30 April 2025 and 30 July 2025 relating to the €35 billion Global Covered Bond Programme of Santander UK plc (the "Issuer") (the "Programme"), (the "Prospectus") and comprises a supplementary prospectus for the purposes of Article 23 of Regulation (EU) 2017/1129 as it forms part of domestic law of the United Kingdom by virtue of the European Union (Withdrawal) Act 2018, as amended, varied, superseded or substituted from time to time (the "UK Prospectus Regulation").

Unless otherwise defined herein, capitalised terms used in this Supplement have the meanings given to them in the Prospectus.

This Supplement has been approved by the United Kingdom Financial Conduct Authority (the "FCA"), which is the competent authority for the purposes of the UK Prospectus Regulation. The FCA only approves this Supplement as meeting the standards of completeness, comprehensibility and consistency imposed by the UK Prospectus Regulation, and such approval should not be considered as an endorsement of the Issuer that is the subject of this Supplement.

The Issuer and Abbey Covered Bonds LLP (the "LLP") (each an "Obligor") accept responsibility for the information contained in this Supplement. To the best of the knowledge of each Obligor (each having taken all reasonable care to ensure that such is the case) the information contained in this Supplement is in accordance with the facts and does not omit anything likely to affect the import of such information.

This Supplement has been prepared for the purpose of incorporating by reference into the Prospectus the unaudited half yearly financial report of the Issuer in respect of the six months ended 30 June 2025 (the "Santander UK plc 2025 Half Yearly Financial Report"), as set out in further detail below.

Any non-incorporated parts of a document referred to herein are either deemed not relevant for an investor or are otherwise covered elsewhere in the Prospectus, to which this Supplement relates.

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

If any document which is incorporated by reference itself incorporates any information or other documents therein, either expressly or implicitly, such information or other documents will not form part of this Supplement or the Prospectus for the purposes of the Prospectus Regulation except where such information or other documents are specifically incorporated by reference or attached to this Supplement.

Any information in the documents incorporated by reference which is not incorporated in and does not form part of this Supplement is not relevant for investors or is contained elsewhere in the Prospectus to which this Supplement relates.

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

Publication of Half Yearly Financial Report

On 29 August 2025, the Issuer published the Santander UK plc 2025 Half Yearly Financial Report, which is incorporated in, and forms part of, the Prospectus.

A copy of the Santander UK plc 2025 Half Yearly Financial Report has been submitted to the National Storage Mechanism and is available for viewing at: https://data.fca.org.uk/#/nsm/nationalstoragemechanism.

The Santander UK plc 2025 Half Yearly Financial Report is available for viewing at: https://www.santander.co.uk/aboutsantander/investor-relations/santander-uk-plc

This Supplement will be published on the website of the London Stock Exchange at the following link: http://www.londonstockexchange.com/exchange/news/market-news/market-news-home.html.