Condensed Consolidated Statements of Shareholders’ Equity $ in Thousands	USD ($) shares	2021 Award USD ($)	2020 Award USD ($)	ADDITIONAL PAID-IN CAPITAL USD ($)	ADDITIONAL PAID-IN CAPITAL 2021 Award USD ($)	ADDITIONAL PAID-IN CAPITAL 2020 Award USD ($)	ACCUMULATED OTHER COMPREHENSIVE INCOME USD ($)	ACCUMULATED DEFICIT USD ($)	Ordinary shares £ / shares shares	Ordinary shares Common stock USD ($) shares	Ordinary shares Common stock 2021 Award USD ($) shares	Ordinary shares Common stock 2020 Award USD ($) shares	Deferred shares £ / shares shares	Deferred shares Common stock USD ($) shares
Beginning balance (in shares) at Dec. 31, 2020 | shares										35,930,331				1
Beginning balance at Dec. 31, 2020	$ 196,561			$ 279,480			$ 14,585	$ (97,899)		$ 367				$ 28
Exercise of share options (in shares) | shares											581,328	232,227
Exercise of share options		$ 998	$ 0		$ 992	$ (3)					$ 6	$ 3
Share-based compensation expense	1,666			1,666
Unrealized gain (loss) on foreign currency translation	1,988						1,988
Net loss	(12,715)							(12,715)
Ending balance (in shares) at Mar. 31, 2021 | shares										36,743,886				1
Ending balance at Mar. 31, 2021	188,498			282,135			16,573	(110,614)		$ 376				$ 28
Beginning balance (in shares) at Dec. 31, 2020 | shares										35,930,331				1
Beginning balance at Dec. 31, 2020	196,561			279,480			14,585	(97,899)		$ 367				$ 28
Exercise of share options (in shares) | shares										1,165,004		232,227
Net loss	(30,243)
Ending balance (in shares) at Jun. 30, 2021 | shares										41,695,335				1
Ending balance at Jun. 30, 2021	327,360			438,825			16,218	(128,142)		$ 431				$ 28
Beginning balance (in shares) at Mar. 31, 2021 | shares										36,743,886				1
Beginning balance at Mar. 31, 2021	188,498			282,135			16,573	(110,614)		$ 376				$ 28
Issuance of ordinary shares, net of issuance costs (in shares) | shares										4,600,000
Issuance of ordinary shares, net of issuance costs	154,794			154,743						$ 51
Exercise of share options (in shares) | shares										351,449
Exercise of share options	47			43						$ 4
Share-based compensation expense	1,904			1,904
Unrealized gain (loss) on foreign currency translation	(355)						(355)
Net loss	(17,528)							(17,528)
Ending balance (in shares) at Jun. 30, 2021 | shares										41,695,335				1
Ending balance at Jun. 30, 2021	327,360			438,825			16,218	(128,142)		$ 431				$ 28
Common stock, par value (in GBP per share) | £ / shares									£ 0.008				£ 21,921.504
Beginning balance (in shares) at Dec. 31, 2021 | shares									42,019,874	42,019,874			1	1
Beginning balance at Dec. 31, 2021	284,412			444,750			8,840	(169,641)		$ 435				$ 28
Exercise of share options (in shares) | shares										376,158
Exercise of share options	397			393						$ 4
Vesting of restricted stock units (in shares) | shares										68,534
Vesting of restricted stock units	1									$ 1
Share-based compensation expense	3,128			3,128
Unrealized gain (loss) on foreign currency translation	(7,193)						(7,193)
Net loss	(21,171)							(21,171)
Ending balance (in shares) at Mar. 31, 2022 | shares										42,464,566				1
Ending balance at Mar. 31, 2022	259,574			448,271			1,647	(190,812)		$ 440				$ 28
Beginning balance (in shares) at Dec. 31, 2021 | shares									42,019,874	42,019,874			1	1
Beginning balance at Dec. 31, 2021	$ 284,412			444,750			8,840	(169,641)		$ 435				$ 28
Exercise of share options (in shares) | shares	431,885									431,885
Vesting of restricted stock units (in shares) | shares										70,638
Net loss	$ (42,208)
Ending balance (in shares) at Jun. 30, 2022 | shares									42,522,397	42,522,397			1	1
Ending balance at Jun. 30, 2022	224,585			451,453			(15,487)	(211,849)		$ 440				$ 28
Beginning balance (in shares) at Mar. 31, 2022 | shares										42,464,566				1
Beginning balance at Mar. 31, 2022	259,574			448,271			1,647	(190,812)		$ 440				$ 28
Exercise of share options (in shares) | shares										55,727
Exercise of share options	4			4
Vesting of restricted stock units (in shares) | shares										2,104
Vesting of restricted stock units	0
Share-based compensation expense	3,178			3,178
Unrealized gain (loss) on foreign currency translation	(17,134)						(17,134)
Net loss	(21,037)							(21,037)
Ending balance (in shares) at Jun. 30, 2022 | shares									42,522,397	42,522,397			1	1
Ending balance at Jun. 30, 2022	$ 224,585			$ 451,453			$ (15,487)	$ (211,849)		$ 440				$ 28
Common stock, par value (in GBP per share) | £ / shares									£ 0.008				£ 21,921.504