SECURITISATIONS AND COVERED BONDS - Narrative (Details) - Securitisation programmes - GBP (£) £ in Millions	Dec. 31, 2021	Dec. 31, 2020
SECURITISATIONS AND COVERED BONDS (Details) - Narrative [Line Items]
Cash deposits held restricted in use to securitisation and covered bonds	£ 3,558	£ 3,930
Maximum exposure to loss from interests in structured entities	£ 52	£ 52

The amount that best represents the entity's maximum exposure to loss from its interests in structured entities. [Refer: Unconsolidated structured entities [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2021-01-01
-Paragraph 29
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=12&code=ifrs-tx-2021-en-r&anchor=para_29_c&doctype=Standard
-URIDate 2021-03-24

Name:	ifrs-full_MaximumExposureToLossFromInterestsInStructuredEntities
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant