Income taxes (Details) - GBP (£) £ in Thousands	3 Months Ended
Apr. 30, 2018	Apr. 30, 2017
Disclosure Of Income Tax [Abstract]
Current period research and development tax credit receivable on qualifying expenditure	£ 1,036	£ 1,218
Tax expense related to the US operations	(90)	(15)
Total credit for the period	£ 946	£ 1,203

The amount that represents the difference between the tax expense (income) and the product of the accounting profit multiplied by the applicable tax rate(s) that relates to foreign tax rates. [Refer: Accounting profit]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2017-01-01
-Paragraph 81
-Subparagraph c
-Clause i
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=12&date=2017-03-01&anchor=para_81_c_i&doctype=Standard
-URIDate 2017-03-09

Name:	ifrs-full_TaxEffectOfForeignTaxRates
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration