v3.25.4
Retirement benefits - Narrative (Details)
£ in Millions
 12 Months Ended
Jul. 01, 2025
GBP (£)
Dec. 31, 2025
GBP (£)
director
contract
Dec. 31, 2024
GBP (£)
Dec. 31, 2023
GBP (£)
Sep. 30, 2024
GBP (£)
Disclosure of net defined benefit liability (asset) [line items]          
Current service cost   £ 122 £ 150 £ 119  
Surplus in plan   £ 3,083 3,099    
Number of longevity reinsurance contracts | contract   2      
Percentage of current pensioner liabilities covered   70.00%      
Director          
Disclosure of net defined benefit liability (asset) [line items]          
Number of directors on trustee board | director   6      
Independent director          
Disclosure of net defined benefit liability (asset) [line items]          
Number of directors on trustee board | director   3      
Member nominated director          
Disclosure of net defined benefit liability (asset) [line items]          
Number of directors on trustee board | director   3      
Fair value of plan assets          
Disclosure of net defined benefit liability (asset) [line items]          
Benefits paid   £ (1,189) (1,221)    
Fair value of plan assets | Barclays Bank PLC          
Disclosure of net defined benefit liability (asset) [line items]          
Equity instruments   0 0    
Bonds   0 0    
Retirement benefit obligations          
Disclosure of net defined benefit liability (asset) [line items]          
Current service cost   135 168    
Benefits paid   1,197 1,226    
UKRF | UK          
Disclosure of net defined benefit liability (asset) [line items]          
Current service cost   135      
UKRF | UK | Barclays Bank UK PLC          
Disclosure of net defined benefit liability (asset) [line items]          
Current service cost   9      
UKRF | UK | Barclays Execution Services          
Disclosure of net defined benefit liability (asset) [line items]          
Current service cost   4      
Section 75 Contribution Plan          
Disclosure of net defined benefit liability (asset) [line items]          
Defined benefit contributions paid   0 0    
Pension defined benefit plans | Foreign countries | Retirement benefit obligations          
Disclosure of net defined benefit liability (asset) [line items]          
Defined benefit obligation, at present value   £ 703 £ 695    
Pension defined benefit plans | UKRF | UK          
Disclosure of net defined benefit liability (asset) [line items]          
Scheme as a percentage of total retirement benefit obligations   96.00% 96.00%    
Increase (decrease) in net defined benefit liability (asset) resulting from transfer to a separate pension plan £ 53        
Surplus in plan   £ 3,181 £ 3,199   £ 1,750
Benefits paid   1,158 1,189    
Transfers out of the fund and contribution refunds   £ 145 £ 165    
Percentage of longevity risk for current pensioners reinsured   70.00%      
Estimate of contributions expected to be paid to plan for next annual reporting period   £ 11      
Pension defined benefit plans | UKRF | UK | Actuarial assumption of key financial assumptions          
Disclosure of net defined benefit liability (asset) [line items]          
Assumption for future inflation increase (decrease)   (0.20%)      
Future mortality improvement percentage   1.10% 1.25%    
Pension defined benefit plans | UKRF | UK | Barclays Bank PLC          
Disclosure of net defined benefit liability (asset) [line items]          
Maximum funding deficit secured by collateral pool   £ 8,400      
Pension defined benefit plans | UKRF | UK | Barclays Bank PLC | Bottom of range          
Disclosure of net defined benefit liability (asset) [line items]          
Percentage of funding deficit secured by collateral pool   100.00%      
Pension defined benefit plans | UKRF | UK | Fair value of plan assets          
Disclosure of net defined benefit liability (asset) [line items]          
Increase (decrease) in net defined benefit liability (asset) resulting from transfer to a separate pension plan 750        
Benefits paid   £ (1,158) £ (1,189)    
Percentage of fair value of scheme assets invested in liability driven investment strategies   39.00%      
Pension defined benefit plans | UKRF | UK | Retirement benefit obligations          
Disclosure of net defined benefit liability (asset) [line items]          
Increase (decrease) in net defined benefit liability (asset) resulting from transfer to a separate pension plan £ 697        
Current service cost   £ 120 £ 155    
Weighted average duration of the benefit payments reflected in defined benefit obligation, UKRF   11 years 11 years    
Duration of expected benefits are projected to be paid out   50 years      
Benefits paid   £ 1,158 £ 1,189    
Pension defined benefit plans | UKRF | UK | Retirement benefit obligations | Within 10 years          
Disclosure of net defined benefit liability (asset) [line items]          
Percentage of benefits are expected to be paid   35.00%      
Pension defined benefit plans | UKRF | UK | Retirement benefit obligations | In years 11 to 20          
Disclosure of net defined benefit liability (asset) [line items]          
Percentage of benefits are expected to be paid   34.00%      
Pension defined benefit plans | UKRF | UK | Retirement benefit obligations | In years 20 to 30          
Disclosure of net defined benefit liability (asset) [line items]          
Percentage of benefits are expected to be paid   20.00%      
Post-employment medical defined benefit plans | Other | Retirement benefit obligations          
Disclosure of net defined benefit liability (asset) [line items]          
Defined benefit obligation, at present value   £ 98 £ 99