v3.25.2
Credit risk - Disclosure of management adjustments to models for impairment (Details) - GBP (£)
£ in Millions
Jun. 30, 2025
Dec. 31, 2024
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Proportion of Management adjustments to Total impairment allowance 0.60% (0.80%)
Total loans and advances at amortised cost    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Proportion of Management adjustments to Total impairment allowance 0.60% (0.60%)
Total loans and advances at amortised cost | Assets classified as held for sale    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Proportion of Management adjustments to Total impairment allowance 2.40% 6.70%
Retail credit cards    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Proportion of Management adjustments to Total impairment allowance 1.20% (0.90%)
Retail credit cards | Assets classified as held for sale | Co-branded card portolio    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Proportion of Management adjustments to Total impairment allowance 2.50% 0.00%
Retail credit cards | Assets classified as held for sale | German Consumer Finance portfolio    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Proportion of Management adjustments to Total impairment allowance 0.00% 13.70%
Retail other    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Proportion of Management adjustments to Total impairment allowance 0.00% 11.10%
Retail other | Assets classified as held for sale | German Consumer Finance portfolio    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Proportion of Management adjustments to Total impairment allowance 0.00% 17.50%
Corporate loans    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Proportion of Management adjustments to Total impairment allowance (1.00%) (0.50%)
Corporate loans | Assets classified as held for sale | Co-branded card portolio    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Proportion of Management adjustments to Total impairment allowance 0.00% 0.00%
Impairment allowance | Total impairment allowance    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets £ 3,677 £ 3,860
Impairment allowance | Impairment allowance pre management adjustments    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 3,655 3,889
Impairment allowance | Management adjustments    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 22 (29)
Impairment allowance | Economic uncertainty adjustments    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 79 0
Impairment allowance | Economic uncertainty adjustments | Assets classified as held for sale    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 6 0
Impairment allowance | Other adjustments    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets (57) (29)
Impairment allowance | Total loans and advances at amortised cost | Assets classified as held for sale    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 240 489
Impairment allowance | Total loans and advances at amortised cost | Total impairment allowance    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 3,656 3,840
Impairment allowance | Total loans and advances at amortised cost | Total impairment allowance | Assets classified as held for sale    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 245 496
Impairment allowance | Total loans and advances at amortised cost | Impairment allowance pre management adjustments    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 3,635 3,862
Impairment allowance | Total loans and advances at amortised cost | Impairment allowance pre management adjustments | Assets classified as held for sale    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 239 463
Impairment allowance | Total loans and advances at amortised cost | Management adjustments    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 21 (22)
Impairment allowance | Total loans and advances at amortised cost | Management adjustments | Assets classified as held for sale    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 6 33
Impairment allowance | Total loans and advances at amortised cost | Economic uncertainty adjustments    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 78 0
Impairment allowance | Total loans and advances at amortised cost | Economic uncertainty adjustments | Assets classified as held for sale    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 6 0
Impairment allowance | Total loans and advances at amortised cost | Other adjustments    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets (57) (22)
Impairment allowance | Total loans and advances at amortised cost | Other adjustments | Assets classified as held for sale    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 0 33
Impairment allowance | Retail credit cards    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 2,371 2,557
Impairment allowance | Retail credit cards | Assets classified as held for sale | Co-branded card portolio    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 236 271
Impairment allowance | Retail credit cards | Assets classified as held for sale | German Consumer Finance portfolio    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 0 116
Impairment allowance | Retail credit cards | Total impairment allowance    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 2,417 2,607
Impairment allowance | Retail credit cards | Total impairment allowance | Assets classified as held for sale | Co-branded card portolio    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 241 277
Impairment allowance | Retail credit cards | Total impairment allowance | Assets classified as held for sale | German Consumer Finance portfolio    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 0 117
Impairment allowance | Retail credit cards | Impairment allowance pre management adjustments    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 2,387 2,630
Impairment allowance | Retail credit cards | Impairment allowance pre management adjustments | Assets classified as held for sale | Co-branded card portolio    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 235 277
Impairment allowance | Retail credit cards | Impairment allowance pre management adjustments | Assets classified as held for sale | German Consumer Finance portfolio    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 0 101
Impairment allowance | Retail credit cards | Management adjustments    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 30 (23)
Impairment allowance | Retail credit cards | Management adjustments | Assets classified as held for sale | Co-branded card portolio    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 6 0
Impairment allowance | Retail credit cards | Management adjustments | Assets classified as held for sale | German Consumer Finance portfolio    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 0 16
Impairment allowance | Retail credit cards | Economic uncertainty adjustments    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 30 0
Impairment allowance | Retail credit cards | Economic uncertainty adjustments | Assets classified as held for sale | Co-branded card portolio    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 6 0
Impairment allowance | Retail credit cards | Economic uncertainty adjustments | Assets classified as held for sale | German Consumer Finance portfolio    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 0 0
Impairment allowance | Retail credit cards | Other adjustments    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 0 (23)
Impairment allowance | Retail credit cards | Other adjustments | Assets classified as held for sale | Co-branded card portolio    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 0 0
Impairment allowance | Retail credit cards | Other adjustments | Assets classified as held for sale | German Consumer Finance portfolio    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 0 16
Impairment allowance | Retail other    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 35 31
Impairment allowance | Retail other | Assets classified as held for sale | German Consumer Finance portfolio    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 0 97
Impairment allowance | Retail other | Total impairment allowance    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 37 36
Impairment allowance | Retail other | Total impairment allowance | Assets classified as held for sale | German Consumer Finance portfolio    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 0 97
Impairment allowance | Retail other | Impairment allowance pre management adjustments    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 37 32
Impairment allowance | Retail other | Impairment allowance pre management adjustments | Assets classified as held for sale | German Consumer Finance portfolio    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 0 80
Impairment allowance | Retail other | Management adjustments    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 0 4
Impairment allowance | Retail other | Management adjustments | Assets classified as held for sale | German Consumer Finance portfolio    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 0 17
Impairment allowance | Retail other | Economic uncertainty adjustments    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 0 0
Impairment allowance | Retail other | Economic uncertainty adjustments | Assets classified as held for sale | German Consumer Finance portfolio    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 0 0
Impairment allowance | Retail other | Other adjustments    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 0 4
Impairment allowance | Retail other | Other adjustments | Assets classified as held for sale | German Consumer Finance portfolio    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 0 17
Impairment allowance | Corporate loans    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 818 791
Impairment allowance | Corporate loans | Assets classified as held for sale | Co-branded card portolio    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 4 5
Impairment allowance | Corporate loans | Total impairment allowance    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 1,175 1,156
Impairment allowance | Corporate loans | Total impairment allowance | Assets classified as held for sale | Co-branded card portolio    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 4 5
Impairment allowance | Corporate loans | Impairment allowance pre management adjustments    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 1,187 1,162
Impairment allowance | Corporate loans | Impairment allowance pre management adjustments | Assets classified as held for sale | Co-branded card portolio    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 4 5
Impairment allowance | Corporate loans | Management adjustments    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets (12) (6)
Impairment allowance | Corporate loans | Management adjustments | Assets classified as held for sale | Co-branded card portolio    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 0 0
Impairment allowance | Corporate loans | Economic uncertainty adjustments    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 48 0
Impairment allowance | Corporate loans | Economic uncertainty adjustments | Assets classified as held for sale | Co-branded card portolio    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets 0 0
Impairment allowance | Corporate loans | Other adjustments    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets (60) (6)
Impairment allowance | Corporate loans | Other adjustments | Assets classified as held for sale | Co-branded card portolio    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Financial assets £ 0 £ 0