v3.26.1
Post employment benefits - Weighted average assumptions used to determine group's deficit/surplus in main post employment plans (Details)
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2024
United Kingdom      
Disclosure of defined benefit plans [line items]      
Rate of general increase in salaries 3.40% 3.30% 3.60%
Rate of increase to pensions in payment 2.60% 2.50% 2.80%
Rate of increase to deferred pensions 2.40% 2.30% 2.60%
Discount rate for plan liabilities 6.00% 5.60% 5.10%
United Kingdom | CPI      
Disclosure of defined benefit plans [line items]      
Inflation 2.40% 2.30% 2.60%
United Kingdom | RPI      
Disclosure of defined benefit plans [line items]      
Inflation 2.90% 2.80% 3.10%
Ireland      
Disclosure of defined benefit plans [line items]      
Rate of general increase in salaries 3.50% 3.40% 3.70%
Rate of increase to pensions in payment 2.00% 2.00% 2.20%
Rate of increase to deferred pensions 2.00% 2.00% 2.20%
Discount rate for plan liabilities 4.10% 3.80% 3.60%
Ireland | CPI      
Disclosure of defined benefit plans [line items]      
Inflation 2.10% 2.00% 2.30%
United States      
Disclosure of defined benefit plans [line items]      
Rate of general increase in salaries 0.00% 0.00% 0.00%
Rate of increase to pensions in payment 0.00% 0.00% 0.00%
Rate of increase to deferred pensions 0.00% 0.00% 0.00%
Discount rate for plan liabilities 5.40% 5.20% 5.30%
United States | CPI      
Disclosure of defined benefit plans [line items]      
Inflation 2.30% 2.30% 2.30%