Structured entities - Carrying amount of interest held in unconsolidated structured entities (Details) - GBP (£) £ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022
Collective investment vehicles and limited partnerships
STRUCTURED ENTITIES (Details) - Narrative [Line Items]
Carrying amount	£ (76,426)	£ (68,913)
Securitisation vehicles
STRUCTURED ENTITIES (Details) - Narrative [Line Items]
Carrying amount	(4,127)	0
Interest rate derivatives provided to securitisation vehicles
STRUCTURED ENTITIES (Details) - Narrative [Line Items]
Carrying amount	£ (17)	£ 0

The amount of losses incurred by the entity relating to its interests in structured entities. [Refer: Unconsolidated structured entities [member]]

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IFRS
-Number 12
-IssueDate 2023-01-01
-Paragraph B26
-Subparagraph b
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=12&code=ifrs-tx-2023-en-r&anchor=para_B26_b&doctype=Appendix&subtype=B
-URIDate 2023-03-23

Name:	ifrs-full_LossesIncurredInRelationToInterestsInStructuredEntities
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration