Pensions and other post-retirement benefits - Schedule of reconciliation of the net defined benefit asset (Details) - GBP (£) £ in Millions |
6 Months Ended | |
|---|---|---|
Sep. 30, 2025 |
Sep. 30, 2024 |
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| Employee Benefits [Abstract] | ||
| Opening net defined benefit asset | £ 1,916 | £ 1,814 |
| Changes in net defined benefit liability (asset) [abstract] | ||
| Cost recognised in the income statement | (25) | (29) |
| Employer contributions | 62 | 81 |
| Remeasurements and foreign exchange | 260 | 18 |
| Other movements | 2 | (9) |
| Adjustments for restrictions on the defined benefit asset | (140) | 0 |
| Closing net defined benefit asset | £ 2,075 | £ 1,875 |
| X | ||||||||||
- References No definition available.
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| X | ||||||||||
- Definition The decrease (increase) in net defined benefit liability (asset) resulting from contributions to a defined benefit plan by the employer. [Refer: Net defined benefit liability (asset); Defined benefit plans [domain]] Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition The decrease (increase) in a net defined benefit liability (asset) resulting from the remeasurement of that net defined benefit liability (asset). [Refer: Net defined benefit liability (asset)] Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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| X | ||||||||||
- Definition The increase (decrease) in the net defined benefit liability (asset) resulting from changes that the entity does not separately disclose in the same statement or note. [Refer: Net defined benefit liability (asset)] Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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| X | ||||||||||
- Definition The amount of deficit or surplus in a defined benefit plan, adjusted for any effect of limiting a net defined benefit asset to the asset ceiling. [Refer: Defined benefit plans [domain]] Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition Adjustments For Restrictions On Defined Benefit Asset No definition available.
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| X | ||||||||||
- Definition Employee Benefits [Abstract] No definition available.
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