Statement of cash flows - Schedule of cash flow on acquisition (Detail) - GBP (£) £ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of cash flow
Purchase of businesses	£ (108)	£ (373)	£ (235)
Deferred payments relating to prior year acquisitions	(16)	(21)	(19)
Total	£ (124)	£ (394)	£ (254)

The aggregate cash flows used in obtaining control of subsidiaries or other businesses, classified as investing activities. [Refer: Subsidiaries [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 7
-IssueDate 2023-01-01
-Paragraph 39
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=7&code=ifrs-tx-2023-en-r&anchor=para_39&doctype=Standard
-URIDate 2023-03-23

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