Equity - Allotted and fully paid share capital (Detail) - GBP (£) £ in Millions, shares in Millions	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2017
Disclosure of reserves within equity [abstract]
Number of shares (in shares)	2,601	2,695	2,754
Nominal value	£ 753	£ 780	£ 797

The number of shares issued by the entity, for which full payment has been received.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2018-01-01
-Paragraph 79
-Subparagraph a
-Clause ii
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_79_a_ii&doctype=Standard
-URIDate 2018-03-16

Name:	ifrs-full_NumberOfSharesIssuedAndFullyPaid
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant