Operating Expenses - Additional Information (Detail) - GBP (£) £ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2025 |
Dec. 31, 2024 |
Dec. 31, 2023 |
|
| Operating expense [line items] | |||
| Research and efficacy costs | £ 8 | £ 6 | £ 8 |
| Auditor's remuneration for other services | 0 | 0 | 0 |
| Impairment Loss Recognised In Profit Or Loss Product development | 87 | 0 | 0 |
| Adjustments for impairment loss (reversal of impairment loss) recognised in profit or loss, property, plant and equipment | 25 | 0 | 11 |
| Expense of restructuring activities | 0 | 2 | 0 |
| Classification of assets as held for sale [member] | |||
| Operating expense [line items] | |||
| Reversal of impairment loss | 3 | 0 | 0 |
| Severance and Impairment of RightofUse Property Assets [Member] | |||
| Operating expense [line items] | |||
| Expense of restructuring activities | £ 0 | £ 2 | £ 0 |