Fair value of financial instruments - Fair value adjustments (Details) - Significant unobservable inputs (Level 3) - GBP (£) £ in Millions |
Jun. 30, 2026 |
Dec. 31, 2025 |
|---|---|---|
| Exit price adjustments derived from market bid-offer spreads | ||
| Disclosure of detailed information about financial instruments [line items] | ||
| Fair value adjustments | £ (715) | £ (628) |
| Uncollateralised derivative funding | ||
| Disclosure of detailed information about financial instruments [line items] | ||
| Fair value adjustments | 49 | 62 |
| Derivative credit valuation adjustments | ||
| Disclosure of detailed information about financial instruments [line items] | ||
| Fair value adjustments | (162) | (155) |
| Derivative debit valuation adjustments | ||
| Disclosure of detailed information about financial instruments [line items] | ||
| Fair value adjustments | £ 103 | £ 119 |