v3.26.1
Property, plant and equipment - Disclosure of movements of right-of-use assets (Details) - GBP (£)
£ in Millions
 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Disclosure of quantitative information about right-of-use assets [line items]    
Right-of-use assets, beginning balance £ 773 £ 728
Exchange adjustments (14) (15)
Additions 222 200
Reclassification to held for sale (note 10)   (17)
Disposals (13) (3)
Depreciation charge for the year (132) (120)
Right-of-use assets, ending balance 836 773
Land and buildings    
Disclosure of quantitative information about right-of-use assets [line items]    
Right-of-use assets, beginning balance 303 293
Exchange adjustments (6) (6)
Additions 23 39
Reclassification to held for sale (note 10)   (2)
Disposals (11) 0
Depreciation charge for the year (24) (21)
Right-of-use assets, ending balance 285 303
Plant and machinery    
Disclosure of quantitative information about right-of-use assets [line items]    
Right-of-use assets, beginning balance 101 128
Exchange adjustments (2) (2)
Additions 0 2
Reclassification to held for sale (note 10)   (15)
Disposals 0 0
Depreciation charge for the year (6) (12)
Right-of-use assets, ending balance 93 101
Assets in the course of construction    
Disclosure of quantitative information about right-of-use assets [line items]    
Right-of-use assets, beginning balance 0 0
Exchange adjustments 0 0
Additions 0 0
Reclassification to held for sale (note 10)   0
Disposals 0 0
Depreciation charge for the year 0 0
Right-of-use assets, ending balance 0 0
Motor vehicles and office equipment    
Disclosure of quantitative information about right-of-use assets [line items]    
Right-of-use assets, beginning balance 369 307
Exchange adjustments (6) (7)
Additions 199 159
Reclassification to held for sale (note 10)   0
Disposals (2) (3)
Depreciation charge for the year (102) (87)
Right-of-use assets, ending balance £ 458 £ 369