Retirement benefit obligations - Principal Assumptions (Details)	Jun. 30, 2026	Dec. 31, 2025
Schedule Of Principal Actuarial And Financial Assumptions Used In Valuations Of Defined Benefit Pension Schemes [Line Items]
Discount rate	6.03%	5.57%
Rate of inflation:
Rate of salary increases	0.00%	0.00%
Weighted-average rate of increase for pensions in payment	2.61%	2.52%
Retail Price Index (RPI)
Rate of inflation:
Prices index	2.77%	2.65%
Consumer Price Index (CPI)
Rate of inflation:
Prices index	2.33%	2.13%

The discount rate used as the significant actuarial assumption to determine the present value of a defined benefit obligation. [Refer: Defined benefit obligation, at present value; Actuarial assumptions [domain]]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 19
-IssueDate 2025-01-01
-Paragraph 144
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-URIDate 2025-03-27

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The expected rate of inflation that is used as a significant actuarial assumption to determine the present value of a defined benefit obligation. [Refer: Defined benefit plans [domain]; Defined benefit obligation, at present value; Actuarial assumptions [domain]]

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The expected rate of increases in pension that is used as a significant actuarial assumption to determine the present value of a defined benefit obligation. [Refer: Defined benefit plans [domain]; Defined benefit obligation, at present value; Actuarial assumptions [domain]]

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The expected rate of salary increases used as a significant actuarial assumption to determine the present value of a defined benefit obligation. [Refer: Defined benefit plans [domain]; Defined benefit obligation, at present value; Actuarial assumptions [domain]]

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Schedule Of Principal Actuarial And Financial Assumptions Used In Valuations Of Defined Benefit Pension Schemes

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