v3.26.1
Fair value of financial instruments - Assets and liabilities held at fair value disaggregated by valuation technique (fair value hierarchy) and balance sheet classification (Details) - GBP (£)
£ in Millions
Jun. 30, 2026
Dec. 31, 2025
Disclosure of detailed information about financial instruments [line items]    
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)
At fair value    
Disclosure of detailed information about financial instruments [line items]    
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
Investment property 42 43
Total assets 772,114 669,798
Trading portfolio liabilities (76,473) (56,829)
Financial liabilities designated at fair value (320,350) (293,527)
Derivative financial instruments (291,770) (240,757)
Total liabilities (688,593) (591,113)
Quoted market prices (Level 1) | At fair value    
Disclosure of detailed information about financial instruments [line items]    
Trading portfolio assets 127,559 110,773
Financial assets at fair value through the income statement 6,446 5,015
Derivative financial instruments 61 108
Financial assets at fair value through other comprehensive income 32,290 31,640
Investment property 0 0
Total assets 166,356 147,536
Trading portfolio liabilities (61,743) (42,009)
Financial liabilities designated at fair value (1,678) (1,702)
Derivative financial instruments (47) (93)
Total liabilities (63,468) (43,804)
Observable inputs (Level 2) | At fair value    
Disclosure of detailed information about financial instruments [line items]    
Trading portfolio assets 72,375 68,623
Financial assets at fair value through the income statement 201,270 173,801
Derivative financial instruments 301,204 250,374
Financial assets at fair value through other comprehensive income 13,726 8,110
Investment property 0 0
Total assets 588,575 500,908
Trading portfolio liabilities (14,651) (14,733)
Financial liabilities designated at fair value (316,195) (286,972)
Derivative financial instruments (288,868) (237,599)
Total liabilities (619,714) (539,304)
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) | At fair value    
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)