LEASES - Additional Information (Details) - GBP (£) £ in Millions	Dec. 31, 2025	Dec. 31, 2024
Leases Disclosure [Abstract]
Future cash flows for leases not yet commenced to which lessee is committed	£ 70	£ 114
Net investment in finance lease	£ 54	£ 59

The gross investment in the finance lease discounted at the interest rate implicit in the lease. Finance lease is a lease that transfers substantially all the risks and rewards incidental to ownership of an underlying asset. Gross investment in the finance lease is the sum of: (a) the lease payments receivable by a lessor under a finance lease; and (b) any unguaranteed residual value accruing to the lessor. Interest rate implicit in the lease is the rate of interest that causes the present value of (a) the lease payments and (b) the unguaranteed residual value to equal to the sum of (i) the fair value of the underlying asset and (ii) the initial direct costs of the lessor.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 16
-IssueDate 2025-01-01
-Paragraph 94
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=16&code=ifrs-tx-2025-en-r&anchor=para_94&doctype=Standard
-URIDate 2025-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective 2027-01-01
-Name IFRS
-Number 19
-IssueDate 2025-01-01
-Paragraph 122
-Subparagraph b
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=19&code=ifrs-tx-2025-en-r&anchor=para_122_b&doctype=Standard
-URIDate 2025-03-27

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective 2027-01-01
-Name IFRS
-Number 19
-IssueDate 2025-01-01
-Paragraph 122
-Subparagraph b
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=19&code=ifrs-tx-2025-en-r&anchor=para_122_b&doctype=Standard
-URIDate 2025-03-27

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