FINANCIAL RISK MANAGEMENT (Details) - Maturities of Assets and Liabilities - GBP (£) £ in Millions	Dec. 31, 2018	Dec. 31, 2017
Disclosure of financial risk management [text block] [Abstract]
Undated subordinated liabilities	£ 27	£ 24

The amount of subordinated liabilities that do not have a specified repayment date. [Refer: Subordinated liabilities]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2018-01-01
-Paragraph 112
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_112_c&doctype=Standard
-URIDate 2018-03-16

Name:	ifrs-full_UndatedSubordinatedLiabilities
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant