Contingent liabilities and commitments - Schedule of Contingent Liabilities (Details) - GBP (£) £ in Millions	Jun. 30, 2019	Dec. 31, 2018
Contingent liabilities
Acceptances and endorsements	£ 74	£ 194
Other items serving as direct credit substitutes	1,042	632
Performance bonds and other transaction-related contingencies	2,462	2,425
Total Contingent liabilities	3,504	3,057
Total contingent liabilities	£ 3,578	£ 3,251

The amount of the estimated financial effect of contingent liabilities. [Refer: Contingent liabilities [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 37
-IssueDate 2018-01-01
-Paragraph 86
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=37&date=2018-03-01&anchor=para_86_a&doctype=Standard
-URIDate 2018-03-16

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