v3.24.1.1.u2
Provisions - Schedule of changes in provisions (Details) - GBP (£)
£ in Millions
 12 Months Ended
Mar. 31, 2024
Mar. 31, 2023
Mar. 31, 2022
Reconciliation of changes in other provisions [abstract]      
Other provisions, beginning balance £ 2,642 £ 2,539  
Exchange adjustments (47) 131  
Additions 772 455  
Unused amounts reversed (125) (62)  
Adjustment for change in discount rate 33 (224)  
Unwinding of discount 102 88  
Utilised (265) (285)  
Reclassification to held for sale (note 10) (3)    
Other provisions, ending balance 3,109 2,642 £ 2,539
Exceptional items      
Reconciliation of changes in other provisions [abstract]      
Changes in environmental provisions (496) 176 0
Environmental      
Reconciliation of changes in other provisions [abstract]      
Other provisions, beginning balance 1,891 1,877  
Exchange adjustments (37) 114  
Additions 600 142  
Unused amounts reversed (18) (38)  
Adjustment for change in discount rate 4 (176)  
Unwinding of discount 85 72  
Utilised (107) (100)  
Reclassification to held for sale (note 10) 0    
Other provisions, ending balance 2,418 £ 1,891 £ 1,877
Real discount rate (in percent)   1.50% 0.50%
Decommissioning      
Reconciliation of changes in other provisions [abstract]      
Other provisions, beginning balance 297 £ 258  
Exchange adjustments (2) 5  
Additions 34 91  
Unused amounts reversed (7) (10)  
Adjustment for change in discount rate 29 (48)  
Unwinding of discount 11 10  
Utilised (9) (9)  
Reclassification to held for sale (note 10) 0    
Other provisions, ending balance 353 297 £ 258
Other      
Reconciliation of changes in other provisions [abstract]      
Other provisions, beginning balance 454 404  
Exchange adjustments (8) 12  
Additions 138 222  
Unused amounts reversed (100) (14)  
Adjustment for change in discount rate 0 0  
Unwinding of discount 6 6  
Utilised (149) (176)  
Reclassification to held for sale (note 10) (3)    
Other provisions, ending balance £ 338 £ 454 £ 404