Inventories and other current intangibles (Details) - GBP (£) £ in Millions	Mar. 31, 2020	Mar. 31, 2019
Subclassifications of assets, liabilities and equities [abstract]
Fuel stocks	£ 151	£ 99
Raw materials and consumables	265	184
Current intangible assets – emission allowances	133	87
Inventories and current intangible assets	549	370
Inventory valuation reserve	£ 21	£ 20

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 2019-01-01
-Paragraph 37
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=2&code=ifrs-tx-2019-en-r&anchor=para_37&doctype=Standard
-URIDate 2019-03-27

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