Tax from continuing operations (Details) - GBP (£) £ in Millions	6 Months Ended	12 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Mar. 31, 2025
Income taxes paid (refund) [abstract]
Tax on exceptional items and remeasurements	£ 208	£ 112
Average effective tax rate	25.20%	16.40%	22.50%

- References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 26
-IssueDate 2025-01-01
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-URIDate 2025-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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+ Details