RETIREMENT BENEFIT PLANS - Additional Information (Details) - GBP (£) £ in Millions |
6 Months Ended | |
|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
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| Disclosure of net defined benefit liability (asset) [abstract] | ||
| Defined contribution expense | £ 41 | £ 39 |
| Defined benefit expense | £ 10 | £ 4 |
| Percentage of defined benefit obligation insured | 20.00% | |
| X | ||||||||||
- References No definition available.
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| X | ||||||||||
- References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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| X | ||||||||||
- References Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition Percentage Of Defined Benefit Obligation Insured No definition available.
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