Retirement benefit obligations - Principal actuarial assumptions (Details) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2025 |
Dec. 31, 2024 |
Dec. 31, 2023 |
|
| United Kingdom | |||
| Disclosure of defined benefit plans [line items] | |||
| Discount rate | 5.50% | 5.50% | 4.50% |
| Future pension increases | 2.80% | 3.00% | 3.00% |
| Inflation (RPI) | 2.90% | 3.20% | 3.10% |
| Inflation (CPI) | 2.40% | 2.70% | 2.50% |
| Life expectancy at age 60, Male | 26 years 10 months 24 days | 26 years 7 months 6 days | 26 years 10 months 24 days |
| Life expectancy at age 60, Female | 29 years 7 months 6 days | 29 years 6 months | 29 years 8 months 12 days |
| Life expectancy at age 60 in 20 years' time, Male | 28 years 6 months | 28 years 1 month 6 days | 28 years 4 months 24 days |
| Life expectancy at age 60 in 20 years' time, Female | 31 years | 30 years 10 months 24 days | 31 years 1 month 6 days |
| United States of America | |||
| Disclosure of defined benefit plans [line items] | |||
| Discount rate | 5.00% | ||
| Life expectancy at age 60, Male | 25 years | ||
| Life expectancy at age 60, Female | 27 years 2 months 12 days | ||
| Life expectancy at age 60 in 20 years' time, Male | 25 years | ||
| Life expectancy at age 60 in 20 years' time, Female | 27 years 7 months 6 days | ||