Derivative financial instruments - Total recognised derivative assets/(liabilities) (Details) - GBP (£) £ in Millions	Jun. 30, 2025	Dec. 31, 2024
Disclosure of detailed information about financial instruments [line items]
Derivative financial assets	£ 280,194	£ 293,530
Derivative financial instruments	(265,376)	(279,415)
Derivatives
Disclosure of detailed information about financial instruments [line items]
Contract notional amount	96,529,153	84,435,447
Fair value
Disclosure of detailed information about financial instruments [line items]
Derivative financial assets	280,194	293,530
Derivative financial instruments	(265,376)	(279,415)
Derivatives in hedge accounting relationships \| Derivatives
Disclosure of detailed information about financial instruments [line items]
Contract notional amount	317,456	310,376
Derivatives in hedge accounting relationships \| Derivatives designated as cash flow hedges \| Derivatives
Disclosure of detailed information about financial instruments [line items]
Contract notional amount	151,346	147,180
Derivatives in hedge accounting relationships \| Derivatives designated as fair value hedges \| Derivatives
Disclosure of detailed information about financial instruments [line items]
Contract notional amount	161,698	159,182
Derivatives in hedge accounting relationships \| Derivatives designated as hedges of net investments \| Derivatives
Disclosure of detailed information about financial instruments [line items]
Contract notional amount	4,412	4,014
Derivatives in hedge accounting relationships \| Fair value
Disclosure of detailed information about financial instruments [line items]
Derivative assets designated in hedge accounting relationships	3,341	2,539
Derivative liabilities designated in hedge accounting relationships	(614)	(820)
Derivatives in hedge accounting relationships \| Fair value \| Derivatives designated as cash flow hedges
Disclosure of detailed information about financial instruments [line items]
Derivative assets designated in hedge accounting relationships	3,070	2,338
Derivative liabilities designated in hedge accounting relationships	(92)	(320)
Derivatives in hedge accounting relationships \| Fair value \| Derivatives designated as fair value hedges
Disclosure of detailed information about financial instruments [line items]
Derivative assets designated in hedge accounting relationships	71	165
Derivative liabilities designated in hedge accounting relationships	(476)	(434)
Derivatives in hedge accounting relationships \| Fair value \| Derivatives designated as hedges of net investments
Disclosure of detailed information about financial instruments [line items]
Derivative assets designated in hedge accounting relationships	200	36
Derivative liabilities designated in hedge accounting relationships	(46)	(66)
Held for trading \| Derivatives
Disclosure of detailed information about financial instruments [line items]
Contract notional amount	96,211,697	84,125,071
Held for trading \| Fair value
Disclosure of detailed information about financial instruments [line items]
Derivative financial assets held for trading	276,853	290,991
Derivative financial liabilities held for trading	(264,762)	(278,595)
Held for trading \| Foreign exchange derivatives \| Derivatives
Disclosure of detailed information about financial instruments [line items]
Contract notional amount	9,404,176	8,517,266
Held for trading \| Foreign exchange derivatives \| Fair value
Disclosure of detailed information about financial instruments [line items]
Derivative financial assets held for trading	96,359	123,724
Derivative financial liabilities held for trading	(93,246)	(116,671)
Held for trading \| Interest rate derivatives \| Derivatives
Disclosure of detailed information about financial instruments [line items]
Contract notional amount	81,608,401	70,905,836
Held for trading \| Interest rate derivatives \| Fair value
Disclosure of detailed information about financial instruments [line items]
Derivative financial assets held for trading	95,461	95,631
Derivative financial liabilities held for trading	(81,613)	(83,967)
Held for trading \| Credit derivatives \| Derivatives
Disclosure of detailed information about financial instruments [line items]
Contract notional amount	1,710,599	1,537,115
Held for trading \| Credit derivatives \| Fair value
Disclosure of detailed information about financial instruments [line items]
Derivative financial assets held for trading	8,471	6,898
Derivative financial liabilities held for trading	(8,994)	(7,455)
Held for trading \| Equity and stock index and commodity derivatives \| Derivatives
Disclosure of detailed information about financial instruments [line items]
Contract notional amount	3,488,521	3,164,854
Held for trading \| Equity and stock index and commodity derivatives \| Fair value
Disclosure of detailed information about financial instruments [line items]
Derivative financial assets held for trading	76,562	64,738
Derivative financial liabilities held for trading	£ (80,909)	£ (70,502)

The amount of financial assets classified as derivative instruments. [Refer: Financial assets; Derivatives [member]]

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The amount of derivative financial assets held for hedging. [Refer: Derivative financial assets]

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The amount of derivative financial assets held for trading. [Refer: Derivative financial assets; Financial assets at fair value through profit or loss, classified as held for trading]

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The amount of financial liabilities classified as derivative instruments. [Refer: Financial assets; Derivatives [member]]

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The amount of derivative financial liabilities held for hedging. [Refer: Derivative financial liabilities]

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The amount of derivative financial liabilities held for trading. [Refer: Derivative financial liabilities; Financial liabilities at fair value through profit or loss that meet definition of held for trading]

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Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with members defined in one or many axes of the table.

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No definition available.

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The nominal or face amount of a financial instrument, used to calculate payments made on that instrument.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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