Net interest income - Narrative (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024		Dec. 31, 2023
Analysis of income and expense [abstract]
Net income statement transfers	£ 1,869	£ 2,597	[1]	£ 1,838	[1]

[1] 1Current tax and deferred tax impacts, previously shown in aggregate for each reserve, are now presented alongside each line item. Comparatives are represented on a consistent basis.