Inventories and current intangible assets - Schedule of inventories and current intangible assets (Details) - GBP (£) £ in Millions	Mar. 31, 2024	Mar. 31, 2023
Subclassifications of assets, liabilities and equities [abstract]
Fuel stocks	£ 188	£ 280
Raw materials and consumables	542	460
Current intangible assets – emission allowances	98	136
Inventories and current intangible assets	£ 828	£ 876

A classification of current inventory representing the amount of current raw materials and current production supplies. [Refer: Current production supplies; Current raw materials]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 2
-IssueDate 2023-01-01
-Paragraph 37
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=2&code=ifrs-tx-2023-en-r&anchor=para_37&doctype=Standard
-URIDate 2023-03-23

Name:	ifrs-full_CurrentRawMaterialsAndCurrentProductionSupplies
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant