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 £ 210,102 £ 190,061
Financial assets at fair value through the income statement 213,100 186,857
Derivative financial instruments 303,602 252,459
Financial assets at fair value through other comprehensive income 83,012 74,394
Trading portfolio liabilities (78,405) (57,737)
Financial liabilities designated at fair value (321,925) (294,108)
Derivative financial instruments (291,785) (240,808)
Fair value    
Disclosure of detailed information about financial instruments [line items]    
Trading portfolio assets 210,102 190,061
Financial assets at fair value through the income statement 213,100 186,857
Derivative financial instruments 303,602 252,459
Financial assets at fair value through other comprehensive income 83,012 74,394
Investment property 42 43
Total assets 809,858 703,814
Trading portfolio liabilities (78,405) (57,737)
Financial liabilities designated at fair value (321,925) (294,108)
Derivative financial instruments (291,785) (240,808)
Total liabilities (692,115) (592,653)
Quoted market prices (Level 1) | Fair value    
Disclosure of detailed information about financial instruments [line items]    
Trading portfolio assets 129,002 111,158
Financial assets at fair value through the income statement 6,666 5,140
Derivative financial instruments 61 108
Financial assets at fair value through other comprehensive income 55,653 51,717
Investment property 0 0
Total assets 191,382 168,123
Trading portfolio liabilities (63,674) (42,917)
Financial liabilities designated at fair value (1,678) (1,702)
Derivative financial instruments (47) (93)
Total liabilities (65,399) (44,712)
Observable inputs (Level 2) | Fair value    
Disclosure of detailed information about financial instruments [line items]    
Trading portfolio assets 72,322 68,556
Financial assets at fair value through the income statement 201,409 173,140
Derivative financial instruments 301,565 250,639
Financial assets at fair value through other comprehensive income 24,918 19,578
Investment property 0 0
Total assets 600,214 511,913
Trading portfolio liabilities (14,652) (14,733)
Financial liabilities designated at fair value (317,749) (287,532)
Derivative financial instruments (288,883) (237,650)
Total liabilities (621,284) (539,915)
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 5,025 8,577
Derivative financial instruments 1,976 1,712
Financial assets at fair value through other comprehensive income 2,441 3,099
Investment property 42 43
Total assets 18,262 23,778
Trading portfolio liabilities (79) (87)
Financial liabilities designated at fair value (2,498) (4,874)
Derivative financial instruments (2,855) (3,065)
Total liabilities (5,432) (8,026)
Significant unobservable inputs (Level 3) | 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 5,025 8,577
Derivative financial instruments 1,976 1,712
Financial assets at fair value through other comprehensive income 2,441 3,099
Investment property 42 43
Total assets 18,262 23,778
Trading portfolio liabilities (79) (87)
Financial liabilities designated at fair value (2,498) (4,874)
Derivative financial instruments (2,855) (3,065)
Total liabilities £ (5,432) £ (8,026)