Other operating expenses - Research and Development - Additional Information (Details) - GBP (£) £ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Expenses by nature [abstract]
Research and development costs including employee benefit costs and depreciation	£ 380	£ 408	£ 323

The amount of expenditure directly attributable to research or development activities, recognised in profit or loss.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 38
-IssueDate 2024-01-01
-Paragraph 126
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=38&code=ifrs-tx-2024-en-r&anchor=para_126&doctype=Standard
-URIDate 2024-03-27

Name:	ifrs-full_ResearchAndDevelopmentExpense
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration