Assets pledged, collateral received and assets transferred - Disclosure of collateral held as security for assets (Details) - GBP (£) £ in Millions	Dec. 31, 2025	Dec. 31, 2024
Assets Pledged, Collateral Received And Assets Transferred [Abstract]
Fair value of securities accepted as collateral	£ 1,511,839	£ 1,317,237
Of which fair value of securities re-pledged/transferred to others	£ 1,389,012	£ 1,193,809

The fair value of collateral held that is permitted to be sold or repledged in the absence of default by the owner of the collateral. [Refer: At fair value [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 7
-IssueDate 2025-01-01
-Paragraph 15
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2025-en-r&anchor=para_15_a&doctype=Standard
-URIDate 2025-03-27

Name:	ifrs-full_AssetsHeldAsCollateralPermittedToBeSoldOrRepledgedAtFairValue
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant