Other financial assets - Additional Information (Detail) - GBP (£) £ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disclosure of financial assets [line items]
Other financial assets	£ 113	£ 138	£ 122
Investments in unlisted securities [member]
Disclosure of financial assets [line items]
Other financial assets	£ 113	£ 138

The amount of non-current financial assets that the entity does not separately disclose in the same statement or note. [Refer: Other financial assets]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2021-01-01
-Paragraph 54
-Subparagraph d
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2021-en-r&anchor=para_54_d&doctype=Standard
-URIDate 2021-03-24

Name:	ifrs-full_OtherNoncurrentFinancialAssets
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant