OTHER RESERVES (Details) - Schedule of Merger Reserve - Hedges of net investment in foreign operations [member] - GBP (£) £ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Merger reserve
Beginning Balance	£ 7,766	£ 7,766	£ 7,976
Redemption of preference shares (note 40)			(210)
Ending Balance	£ 7,766	£ 7,766	£ 7,766

The cash outflow to acquire equity or debt instruments of other entities (other than payments for those instruments considered to be cash equivalents or those held for dealing or trading purposes), classified as investing activities.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 7
-IssueDate 2018-01-01
-Paragraph 16
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=7&date=2018-03-01&anchor=para_16_c&doctype=Standard
-URIDate 2018-03-16

Name:	ifrs-full_OtherCashPaymentsToAcquireEquityOrDebtInstrumentsOfOtherEntitiesClassifiedAsInvestingActivities
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration