v3.24.1.1.u2
Assets held for sale and discontinued operations - Narrative (Details) - GBP (£)
£ in Millions
12 Months Ended
Mar. 31, 2024
Mar. 11, 2024
Jan. 31, 2023
Mar. 31, 2024
Mar. 31, 2023
Mar. 31, 2022
Disclosure of subsidiaries [line items]            
Profit after tax       £ 2,291 £ 7,797 £ 2,354
Total identifiable net assets £ 29,892     29,892 29,562  
Assets and liabilities classified as held for sale            
Disclosure of subsidiaries [line items]            
Net assets held for sale 349     349 1,334  
UK Electricity System Operator            
Disclosure of subsidiaries [line items]            
Profit after tax       178 182 £ (12)
UK Electricity System Operator | Assets and liabilities classified as held for sale            
Disclosure of subsidiaries [line items]            
Total identifiable net assets (293)     (293)    
Net assets held for sale (293)     (293) 0  
RAA option | Assets and liabilities classified as held for sale            
Disclosure of subsidiaries [line items]            
Net assets held for sale £ (47)     £ (47) 0  
GasT TopCo Limited            
Disclosure of subsidiaries [line items]            
Proportion of ownership interest disposed   20.00%        
Cash proceeds   £ 681        
Proportion of ownership interest in associate 20.00% 20.00% 40.00% 20.00%    
Gain on disposal   £ (4)        
GasT TopCo Limited | Discontinued operations            
Disclosure of subsidiaries [line items]            
Dividends received from associates       £ 102    
GasT TopCo Limited | Assets and liabilities classified as held for sale            
Disclosure of subsidiaries [line items]            
Net assets held for sale £ 689     £ 689 £ 1,443  
UK Gas Transmission business            
Disclosure of subsidiaries [line items]            
Proportion of ownership interest disposed     100.00%   60.00%  
Cash proceeds     £ 4,000      
Portion of consideration received consisting of shareholding in acquirer     40.00%      
Associate at fair value     £ 1,400      
Gain on disposal     4,800      
UK Gas Transmission business | Disposal groups classified as held for sale            
Disclosure of subsidiaries [line items]            
Total identifiable net assets     £ 600      
Macquarie Infrastructure and Real Assets (MIRA) and British Columbia Investment Management Corporation (BCI) | GasT TopCo Limited            
Disclosure of subsidiaries [line items]            
Proportion of ownership interest in associate     60.00%