v3.26.1
Fair values of financial assets and liabilities - Schedule of Significant Unobservable Inputs Used in Fair Value Measurement (Details)
£ in Millions
Jun. 30, 2026
GBP (£)
Dec. 31, 2025
GBP (£)
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]    
Financial assets at fair value through profit or loss £ 1,761 £ 2,279
Financial assets at fair value through other comprehensive income 40,365 36,257
Total financial assets carried at fair value 45,214 41,796
Financial liabilities at fair value through profit or loss 4,238 4,243
Derivative financial instruments 4,392 4,286
Total financial liabilities carried at fair value 8,630 8,529
Recurring fair value measurement    
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]    
Financial assets at fair value through profit or loss 249  
Total financial assets carried at fair value 298 337
Derivative financial instruments 107 118
Total financial liabilities carried at fair value 124 135
Recurring fair value measurement | Credit spreads | Discounted cash flows | Securitisation notes and other    
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]    
Financial liabilities at fair value through profit or loss 17 17
Recurring fair value measurement | HPI growth | Market values - property valuation | Shared appreciation rights    
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]    
Derivative financial instruments 101 111
Recurring fair value measurement | Price    
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]    
Financial assets at fair value through profit or loss 12  
Recurring fair value measurement | Interest rate ATM volatility | Option pricing model | Interest rate derivatives    
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]    
Derivative financial instruments £ 6 £ 7
Recurring fair value measurement | Minimum | Credit spreads | Discounted cash flows | Financial liabilities at fair value through profit or loss | Securitisation notes and other    
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]    
Significant unobservable input reasonable assumption, liabilities 0.0349 0.0349
Recurring fair value measurement | Minimum | HPI growth | Market values - property valuation | Derivative financial liabilities | Shared appreciation rights    
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]    
Significant unobservable input reasonable assumption, liabilities 0.03 0.03
Recurring fair value measurement | Minimum | Interest rate ATM volatility | Option pricing model | Derivative financial liabilities | Interest rate derivatives    
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]    
Significant unobservable input reasonable assumption, liabilities 0.0056 0.0038
Recurring fair value measurement | Maximum | Credit spreads | Discounted cash flows | Financial liabilities at fair value through profit or loss | Securitisation notes and other    
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]    
Significant unobservable input reasonable assumption, liabilities 0.0349 0.0349
Recurring fair value measurement | Maximum | HPI growth | Market values - property valuation | Derivative financial liabilities | Shared appreciation rights    
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]    
Significant unobservable input reasonable assumption, liabilities 0.04 0.04
Recurring fair value measurement | Maximum | Interest rate ATM volatility | Option pricing model | Derivative financial liabilities | Interest rate derivatives    
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]    
Significant unobservable input reasonable assumption, liabilities 0.0093 0.0082
Loans and advances to customers | Recurring fair value measurement    
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]    
Financial assets at fair value through profit or loss £ 237 £ 282
Loans and advances to customers | Recurring fair value measurement | Credit spreads | Discounted cash flows    
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]    
Financial assets at fair value through profit or loss 114 147
Loans and advances to customers | Recurring fair value measurement | HPI growth | Market values - property valuation    
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]    
Financial assets at fair value through profit or loss 123 135
Debt securities | Recurring fair value measurement | Credit spreads | Discounted cash flows    
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]    
Financial assets at fair value through other comprehensive income 49 50
Debt securities | Recurring fair value measurement | Price | Discounted cash flows    
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]    
Financial assets at fair value through profit or loss 7  
Equity shares | Recurring fair value measurement | Price | Net asset value    
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]    
Financial assets at fair value through profit or loss £ 5 £ 5
Financial assets at fair value through profit or loss | Loans and advances to customers | Recurring fair value measurement | Minimum | Credit spreads | Discounted cash flows    
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]    
Significant unobservable input, assets 0.0138 0.0138
Financial assets at fair value through profit or loss | Loans and advances to customers | Recurring fair value measurement | Minimum | HPI growth | Market values - property valuation    
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]    
Significant unobservable input, assets 0.03 0.03
Financial assets at fair value through profit or loss | Loans and advances to customers | Recurring fair value measurement | Maximum | Credit spreads | Discounted cash flows    
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]    
Significant unobservable input, assets 0.0349 0.0349
Financial assets at fair value through profit or loss | Loans and advances to customers | Recurring fair value measurement | Maximum | HPI growth | Market values - property valuation    
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]    
Significant unobservable input, assets 0.04 0.04
Financial assets at fair value through profit or loss | Debt securities | Recurring fair value measurement | Minimum | Price | Discounted cash flows    
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]    
Significant unobservable input, assets 0.12  
Financial assets at fair value through profit or loss | Debt securities | Recurring fair value measurement | Maximum | Price | Discounted cash flows    
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]    
Significant unobservable input, assets 0.86  
Financial assets at fair value through other comprehensive income | Debt securities | Recurring fair value measurement | Minimum | Credit spreads | Discounted cash flows    
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]    
Significant unobservable input, assets 0.0287 0.0287
Financial assets at fair value through other comprehensive income | Debt securities | Recurring fair value measurement | Maximum | Credit spreads | Discounted cash flows    
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]    
Significant unobservable input, assets 0.0308 0.0308