Capital Risk - Summary of Regulatory Capital Resources (Details) - GBP (£) £ in Millions |
Jun. 30, 2026 |
Dec. 31, 2025 |
|---|---|---|
| Disclosure Of Regulatory Capital Resources [Line Items] | ||
| CET1 capital | £ 11,370.0 | £ 10,601.0 |
| AT1 capital | 2,060.0 | 1,860.0 |
| Tier 1 capital | 13,430.0 | 12,461.0 |
| Tier 2 capital | 2,370.0 | 1,854.0 |
| Total capital | 15,800.0 | 14,315.0 |
| Transitional IFRS 9 Benefit | ||
| Disclosure Of Regulatory Capital Resources [Line Items] | ||
| Total capital | £ 0.0 | £ 0.0 |