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Share-Based Payments - Summary of Shares Granted under Restricted Share Arrangements (Detail) - Long-term incentive plan [member] - Restricted shares [member]
Unit_pure in Thousands
12 Months Ended
Dec. 31, 2023
GBP (£)
Dec. 31, 2022
GBP (£)
Disclosure of terms and conditions of share-based payment arrangement [line items]    
Number of shares 5,572 7,584
Weighted average fair value £ 6.99 £ 7.61