Financial instruments and risk management - Credit risk - Narrative (Details) £ in Millions, $ in Millions	Jun. 30, 2023 GBP (£)	Jun. 30, 2023 USD ($)	Jun. 30, 2022 GBP (£)	Jun. 30, 2022 USD ($)
Disclosure of detailed information about financial instruments [abstract]
Maximum exposure to credit risk	£ 4,637		£ 5,445
Credit support obligations	£ (15)	$ (19)	£ 19	$ 23

The amount that best represents the maximum exposure to credit risk without taking into account any collateral held or other credit enhancements (for example, netting agreements that do not qualify for offset in accordance with IAS 32). [Refer: Credit risk [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 7
-IssueDate 2022-03-24
-Paragraph 35K
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2022-en-r&anchor=para_35K_a&doctype=Standard
-URIDate 2022-03-24

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2023-01-01
-Name IFRS
-Number 7
-IssueDate 2022-03-24
-Paragraph 36
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2017-en-b&anchor=para_36_a&doctype=Standard&book=b
-URIDate 2022-03-24

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