v3.24.1.1.u2
Goodwill - Narrative (Details) - GBP (£)
£ in Millions
Mar. 31, 2024
Mar. 31, 2023
US Regulated    
Disclosure of reconciliation of changes in goodwill [line items]    
Growth rate used to extrapolate cash flow projections 2.40% 2.50%
UK Electricity Distribution    
Disclosure of reconciliation of changes in goodwill [line items]    
Growth rate used to extrapolate cash flow projections 2.30% 2.60%
UK Electricity Distribution Group    
Disclosure of reconciliation of changes in goodwill [line items]    
Discount rate applied to cash flow projections 5.00% 5.60%
UK Electricity Distribution DNO    
Disclosure of reconciliation of changes in goodwill [line items]    
Discount rate applied to cash flow projections 5.00% 5.60%
New York    
Disclosure of reconciliation of changes in goodwill [line items]    
Discount rate applied to cash flow projections 6.20% 6.40%
New England    
Disclosure of reconciliation of changes in goodwill [line items]    
Discount rate applied to cash flow projections 6.10% 6.60%
National Grid Ventures – US    
Disclosure of reconciliation of changes in goodwill [line items]    
Discount rate applied to cash flow projections 7.20% 8.60%
Accumulated impairment | Goodwill    
Disclosure of reconciliation of changes in goodwill [line items]    
Intangible assets and goodwill £ 0 £ 0