Exercise price per share or per unit of warrants or rights outstanding.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(i)(4))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Value of input used to measure outstanding warrant and right embodying unconditional obligation requiring redemption by transferring asset at specified or determinable date or upon event certain to occur.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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Warrant liability - Unobservable inputs to the fair value measurement of the warrant liability (Details)	Dec. 31, 2019 £ / shares	May 28, 2019 $ / shares £ / shares	Dec. 31, 2018 $ / shares £ / shares
Unobservable inputs to the fair value measurement of the warrant liability
Exercise price of warrants	£ 0.01
Risk free rate \| Series A Warrants
Unobservable inputs to the fair value measurement of the warrant liability
Fair value measurement of the warrant liability		2.2	2.6
Risk free rate \| Series B1 Warrants
Unobservable inputs to the fair value measurement of the warrant liability
Fair value measurement of the warrant liability		2.1	2.5
Expected dividend yield
Unobservable inputs to the fair value measurement of the warrant liability
Fair value measurement of the warrant liability	0
Expected term (years) \| Series A Warrants
Unobservable inputs to the fair value measurement of the warrant liability
Fair value measurement of the warrant liability		8.0	8.4
Expected term (years) \| Series B1 Warrants
Unobservable inputs to the fair value measurement of the warrant liability
Fair value measurement of the warrant liability		5.8	6.25
Expected volatility \| Series A Warrants
Unobservable inputs to the fair value measurement of the warrant liability
Fair value measurement of the warrant liability		74.7	75.4
Expected volatility \| Series B1 Warrants
Unobservable inputs to the fair value measurement of the warrant liability
Fair value measurement of the warrant liability		78.2	79.6
Exercise price \| Series A Warrants
Unobservable inputs to the fair value measurement of the warrant liability
Fair value measurement of the warrant liability		0.01	0.01
Exercise price \| Series B1 Warrants
Unobservable inputs to the fair value measurement of the warrant liability
Fair value measurement of the warrant liability		0.01	0.01
Fair value of preferred shares or ordinary shares underlying the warrant \| Series A Warrants
Unobservable inputs to the fair value measurement of the warrant liability
Fair value measurement of the warrant liability \| $ / shares		12.28	8.61
Fair value of preferred shares or ordinary shares underlying the warrant \| Series B1 Warrants
Unobservable inputs to the fair value measurement of the warrant liability
Fair value measurement of the warrant liability \| $ / shares		12.28	4.15
Probability that the warrants will not be exercisable prior to the IPO \| Series B1 Warrants
Unobservable inputs to the fair value measurement of the warrant liability
Fair value measurement of the warrant liability			50