Earnings per share - Narrative (Details)	Dec. 31, 2025 £ / shares	Dec. 08, 2025 £ / shares	Dec. 07, 2025 £ / shares	Dec. 31, 2024 £ / shares
Earnings per share [abstract]
Share consolidation ratio		0.8889
Nominal value (in pound sterling per share)	£ 3.5	£ 3.5	£ 3.11	£ 3.11

The nominal value per share.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective 2027-01-01
-Name IFRS
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Namespace Prefix:	ifrs-full_
Data Type:	dtr-2022:perShareItemType
Balance Type:	na
Period Type:	instant