v3.24.1.1.u2
Basis of preparation and recent accounting developments (Details)
£ in Millions
12 Months Ended
Mar. 31, 2024
GBP (£)
MW
site
Mar. 11, 2024
Jan. 31, 2023
Mar. 31, 2024
GBP (£)
MW
site
Mar. 31, 2023
GBP (£)
Mar. 31, 2050
GBP (£)
Mar. 31, 2022
GBP (£)
Disclosure of subsidiaries [line items]              
Number of US Superfund sites | site 3     3      
Property, plant and equipment £ 68,907     £ 68,907 £ 64,433    
Other provisions 3,109     3,109 £ 2,642   £ 2,539
Decommissioning provision, ARO              
Disclosure of subsidiaries [line items]              
Other provisions 57     £ 57      
New York              
Disclosure of subsidiaries [line items]              
Cash flow projection, forecast period       5 years      
New England              
Disclosure of subsidiaries [line items]              
Cash flow projection, forecast period       5 years      
Electricity generation plant              
Disclosure of subsidiaries [line items]              
Property, plant and equipment £ 325     £ 325      
Property, plant and equipment, capacity | MW 3,800     3,800      
Liquefied natural gas | Forecast              
Disclosure of subsidiaries [line items]              
Property, plant and equipment           £ 0  
GasT TopCo Limited              
Disclosure of subsidiaries [line items]              
Proportion of ownership interest disposed   20.00%          
Proportion of ownership interest in associate 20.00% 20.00% 40.00% 20.00%      
GasT TopCo Limited | The Consortium              
Disclosure of subsidiaries [line items]              
Proportion of ownership interest in associate   80.00%          
UK Gas Transmission business              
Disclosure of subsidiaries [line items]              
Proportion of ownership interest disposed     100.00%   60.00%    
Minimum | Fixed interest rate bonds              
Disclosure of subsidiaries [line items]              
Notional amount £ 5,600     £ 5,600