v3.26.1
Fair value of financial instruments - Level 3 assets and liabilities held at fair value disaggregated by product type (Details) - GBP (£)
£ in Millions
 6 Months Ended
Jun. 30, 2026
Dec. 31, 2025
Disclosure of detailed information about financial instruments [line items]    
Transfers out of Level 3 of fair value hierarchy, assets £ 3,500  
Transfers out of Level 3 of fair value hierarchy, liabilities (2,300)  
Trading portfolio assets 208,712 £ 189,743
Financial assets at fair value through the income statement 211,836 185,002
Derivative financial instruments 303,238 252,192
Financial assets at fair value through other comprehensive income 48,286 42,818
Trading portfolio liabilities (76,473) (56,829)
Financial liabilities designated at fair value (320,350) (293,527)
Derivative financial instruments (291,770) (240,757)
Significant unobservable inputs (Level 3)    
Disclosure of detailed information about financial instruments [line items]    
Trading portfolio assets 8,778 10,347
Financial assets at fair value through the income statement 4,120 6,186
Derivative financial instruments 1,973 1,710
Financial assets at fair value through other comprehensive income 2,270 3,068
Investment property 42 43
Total assets 17,183 21,354
Trading portfolio liabilities (79) (87)
Financial liabilities designated at fair value (2,477) (4,853)
Derivative financial instruments (2,855) (3,065)
Total liabilities (5,411) (8,005)
Significant unobservable inputs (Level 3) | Interest rate risk    
Disclosure of detailed information about financial instruments [line items]    
Derivative financial instruments 942 759
Total assets 942 759
Derivative financial instruments (1,436) (612)
Total liabilities (1,436) (612)
Significant unobservable inputs (Level 3) | Equity risk    
Disclosure of detailed information about financial instruments [line items]    
Derivative financial instruments 286 520
Total assets 286 520
Derivative financial instruments (424) (1,602)
Total liabilities (424) (1,602)
Significant unobservable inputs (Level 3) | Loans    
Disclosure of detailed information about financial instruments [line items]    
Trading portfolio assets 3,156 5,667
Financial assets at fair value through the income statement 2,979 4,620
Financial assets at fair value through other comprehensive income 2,192 2,235
Total assets 8,327 12,522
Significant unobservable inputs (Level 3) | Corporate debt    
Disclosure of detailed information about financial instruments [line items]    
Trading portfolio assets 1,873 1,849
Financial assets at fair value through the income statement 465 905
Financial assets at fair value through other comprehensive income 60 25
Total assets 2,398 2,779
Trading portfolio liabilities (46) (36)
Total liabilities (46) (36)
Significant unobservable inputs (Level 3) | Asset backed securities    
Disclosure of detailed information about financial instruments [line items]    
Trading portfolio assets 1,670 874
Financial assets at fair value through the income statement 271 188
Financial assets at fair value through other comprehensive income 11 756
Total assets 1,952 1,818
Significant unobservable inputs (Level 3) | Government and Government sponsored debt    
Disclosure of detailed information about financial instruments [line items]    
Trading portfolio assets 1,342 1,513
Financial assets at fair value through the income statement 33 33
Financial assets at fair value through other comprehensive income 7 52
Total assets 1,382 1,598
Trading portfolio liabilities (4) (34)
Total liabilities (4) (34)
Significant unobservable inputs (Level 3) | Private equity investments    
Disclosure of detailed information about financial instruments [line items]    
Financial assets at fair value through the income statement 308 268
Total assets 308 268
Significant unobservable inputs (Level 3) | Issued debt    
Disclosure of detailed information about financial instruments [line items]    
Financial liabilities designated at fair value (2,396) (3,760)
Total liabilities (2,396) (3,760)
Significant unobservable inputs (Level 3) | Reverse repurchase and repurchase agreements    
Disclosure of detailed information about financial instruments [line items]    
Financial assets at fair value through the income statement   97
Total assets   97
Financial liabilities designated at fair value   (887)
Total liabilities   (887)
Significant unobservable inputs (Level 3) | Other products    
Disclosure of detailed information about financial instruments [line items]    
Trading portfolio assets 737 444
Financial assets at fair value through the income statement 64 75
Derivative financial instruments 745 431
Investment property 42 43
Total assets 1,588 993
Trading portfolio liabilities (29) (17)
Financial liabilities designated at fair value (81) (206)
Derivative financial instruments (995) (851)
Total liabilities £ (1,105) £ (1,074)