Finance income and costs (Details) - GBP (£) £ in Millions |
6 Months Ended | |
|---|---|---|
Sep. 30, 2026 |
Sep. 30, 2025 |
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| Finance income [Abstract] | ||
| Interest income from financing activities | £ 40 | £ 126 |
| Net interest on pensions and other post-retirement benefit obligations | 58 | 50 |
| Net gains on financial assets at fair value through profit and loss | 0 | 2 |
| Other interest income | 23 | 30 |
| Finance income | 121 | 208 |
| Interest costs [abstract] | ||
| Interest expense on financial instruments | (1,030) | (999) |
| Unwinding of discount on provisions and other liabilities | (62) | (63) |
| Net gains (losses) on derivatives financial instruments | 4 | (63) |
| Other interest | (18) | (11) |
| Less: interest capitalised | 267 | 189 |
| Finance costs | (839) | (947) |
| Finance income (cost) | (718) | (739) |
| Principal accretion on inflation-linked debt | 86 | 115 |
| Finance income (cost), accretion on inflation-linked swaps | £ 8 | £ 0 |
| Capitalisation rate of borrowing costs eligible for capitalisation | 4.40% | 4.50% |
| Tax relief on capitalised interest | £ 41 | £ 27 |
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- Definition The weighted average of interest and other costs that an entity incurs in connection with the borrowing of funds applicable to the borrowings of the entity that are outstanding during the period, other than borrowings made specifically for the purpose of obtaining a qualifying asset. [Refer: Weighted average [member]; Borrowings] Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- References Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition The gains (losses) on financial assets at fair value through profit or loss. [Refer: Financial assets at fair value through profit or loss] Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- References No definition available.
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- Definition The amount of interest costs that an entity incurs in connection with the borrowing of funds that are directly attributable to the acquisition, construction or production of a qualifying asset and which form part of the cost of that asset. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Finance Cost, Accretion On Inflation-Linked Debt No definition available.
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- Definition Finance Income [Abstract] No definition available.
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- Definition Finance Income (Cost), Accretion On Inflation-Linked Swaps No definition available.
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- Definition Net Losses On Derivatives Financial Instruments, Finance Cost No definition available.
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- Definition Tax Relief On Capitalised Interest No definition available.
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