v3.26.1
PROPERTY, PLANT AND EQUIPMENT (Details) - GBP (£)
£ in Millions
 6 Months Ended
Jun. 30, 2026
Dec. 31, 2025
Disclosure of detailed information about property, plant and equipment [line items]    
Property, plant and equipment including right-of-use assets at beginning of period £ 1,511  
Property, plant and equipment including right-of-use assets at end of period 1,648  
Investment property 16 £ 16
Right-of-use assets    
Disclosure of detailed information about property, plant and equipment [line items]    
Property, plant and equipment including right-of-use assets at end of period 122  
Cost:    
Disclosure of detailed information about property, plant and equipment [line items]    
Property, plant and equipment including right-of-use assets at beginning of period 2,814  
Acquisition of business 145  
Additions 184  
Disposals (186)  
Property, plant and equipment including right-of-use assets at end of period 2,957  
Cost: | Right-of-use assets    
Disclosure of detailed information about property, plant and equipment [line items]    
Property, plant and equipment including right-of-use assets at beginning of period 277  
Acquisition of business 61  
Additions 11  
Disposals (12)  
Property, plant and equipment including right-of-use assets at end of period 337  
Accumulated depreciation and impairment:    
Disclosure of detailed information about property, plant and equipment [line items]    
Property, plant and equipment including right-of-use assets at beginning of period (1,303)  
Charge for the period 83  
Disposals 91  
Property, plant and equipment including right-of-use assets at end of period (1,309)  
Accumulated depreciation and impairment: | Right-of-use assets    
Disclosure of detailed information about property, plant and equipment [line items]    
Property, plant and equipment including right-of-use assets at beginning of period (208)  
Charge for the period 8  
Disposals 1  
Property, plant and equipment including right-of-use assets at end of period (215)  
Accumulated impairment    
Disclosure of detailed information about property, plant and equipment [line items]    
Impairment during the period 14  
Accumulated impairment | Right-of-use assets    
Disclosure of detailed information about property, plant and equipment [line items]    
Impairment during the period 0  
Property    
Disclosure of detailed information about property, plant and equipment [line items]    
Property, plant and equipment including right-of-use assets at end of period 701  
Property | Cost:    
Disclosure of detailed information about property, plant and equipment [line items]    
Property, plant and equipment including right-of-use assets at beginning of period 908  
Acquisition of business 67  
Additions 3  
Disposals (24)  
Property, plant and equipment including right-of-use assets at end of period 954  
Property | Accumulated depreciation and impairment:    
Disclosure of detailed information about property, plant and equipment [line items]    
Property, plant and equipment including right-of-use assets at beginning of period (251)  
Charge for the period 14  
Disposals 20  
Property, plant and equipment including right-of-use assets at end of period (253)  
Property | Accumulated impairment    
Disclosure of detailed information about property, plant and equipment [line items]    
Impairment during the period 8  
Office fixtures and equipment    
Disclosure of detailed information about property, plant and equipment [line items]    
Property, plant and equipment including right-of-use assets at end of period 229  
Office fixtures and equipment | Cost:    
Disclosure of detailed information about property, plant and equipment [line items]    
Property, plant and equipment including right-of-use assets at beginning of period 919  
Acquisition of business 17  
Additions 30  
Disposals (27)  
Property, plant and equipment including right-of-use assets at end of period 939  
Office fixtures and equipment | Accumulated depreciation and impairment:    
Disclosure of detailed information about property, plant and equipment [line items]    
Property, plant and equipment including right-of-use assets at beginning of period (707)  
Charge for the period 28  
Disposals 27  
Property, plant and equipment including right-of-use assets at end of period (710)  
Office fixtures and equipment | Accumulated impairment    
Disclosure of detailed information about property, plant and equipment [line items]    
Impairment during the period 2  
Computer software    
Disclosure of detailed information about property, plant and equipment [line items]    
Property, plant and equipment including right-of-use assets at end of period 0  
Computer software | Cost:    
Disclosure of detailed information about property, plant and equipment [line items]    
Property, plant and equipment including right-of-use assets at beginning of period 6  
Acquisition of business 0  
Additions 0  
Disposals 0  
Property, plant and equipment including right-of-use assets at end of period 6  
Computer software | Accumulated depreciation and impairment:    
Disclosure of detailed information about property, plant and equipment [line items]    
Property, plant and equipment including right-of-use assets at beginning of period (6)  
Charge for the period 0  
Disposals 0  
Property, plant and equipment including right-of-use assets at end of period (6)  
Computer software | Accumulated impairment    
Disclosure of detailed information about property, plant and equipment [line items]    
Impairment during the period 0  
Operating lease assets    
Disclosure of detailed information about property, plant and equipment [line items]    
Property, plant and equipment including right-of-use assets at end of period 596  
Operating lease assets | Cost:    
Disclosure of detailed information about property, plant and equipment [line items]    
Property, plant and equipment including right-of-use assets at beginning of period 704  
Acquisition of business 0  
Additions 140  
Disposals (123)  
Property, plant and equipment including right-of-use assets at end of period 721  
Operating lease assets | Accumulated depreciation and impairment:    
Disclosure of detailed information about property, plant and equipment [line items]    
Property, plant and equipment including right-of-use assets at beginning of period (131)  
Charge for the period 33  
Disposals 43  
Property, plant and equipment including right-of-use assets at end of period (125)  
Operating lease assets | Accumulated impairment    
Disclosure of detailed information about property, plant and equipment [line items]    
Impairment during the period £ 4