Net debt - Schedule of components of net debt (Details) - GBP (£) £ in Millions	Sep. 30, 2026	Mar. 31, 2026
Disclosure of detailed information about financial instruments [line items]
Cash and cash equivalents	£ 308	£ 375
Current financial investments	3,015	2,453
Borrowings and bank overdrafts	(51,222)	(46,755)
Financing derivatives	(700)	(233)
Net debt (net of related derivative financial instruments)	(48,599)	(44,160)
Derivative liabilities	665	180
Derivatives \| Capital expenditure prepayments
Disclosure of detailed information about financial instruments [line items]
Derivative liabilities	£ 82	£ 19

The amount of outstanding funds that the entity is obligated to repay.

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The amount of cash on hand and demand deposits, along with short-term, highly liquid investments that are readily convertible to known amounts of cash and that are subject to an insignificant risk of changes in value. [Refer: Cash; Cash equivalents]

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The amount of net debt of the entity.

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The amount of current financial assets that the entity does not separately disclose in the same statement or note. [Refer: Other financial assets; Current financial assets]

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Derivative Financial Assets (Liabilities)

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Financing Derivatives

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