Condensed Consolidated Statements of Shareholders’ Equity $ in Thousands	USD ($) shares	COMMON STOCK USD ($)	ADDITIONAL PAID-IN CAPITAL USD ($)	ACCUMULATED OTHER COMPREHENSIVE (LOSS)/ INCOME USD ($)	ACCUMULATED DEFICIT USD ($)	Ordinary shares £ / shares shares	Ordinary shares COMMON STOCK USD ($) shares	Deferred shares £ / shares shares	Deferred shares COMMON STOCK USD ($) shares
Shares, par value (in GBP per share) | £ / shares						£ 0.008		£ 21,921.504
Beginning balance (in shares) at Dec. 31, 2021 | shares							42,019,874,000		1,000
Beginning balance at Dec. 31, 2021	$ 284,412		$ 444,750	$ 8,840	$ (169,641)		$ 435		$ 28
Exercise of share options (in shares) | shares							376,158,000
Exercise of share options	397		393				$ 4
Vesting of restricted stock units (in shares) | shares							68,534,000
Vesting of restricted stock units	1						$ 1
Share-based compensation expense	3,128		3,128
Unrealized loss on foreign currency translation	(7,193)			(7,193)
Net loss	(21,171)				(21,171)
Ending balance (in shares) at Mar. 31, 2022 | shares							42,464,566,000		1,000
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							42,019,874,000		1,000
Beginning balance at Dec. 31, 2021	284,412		444,750	8,840	(169,641)		$ 435		$ 28
Exercise of share options (in shares) | shares						431,855
Vesting of restricted stock units (in shares) | shares						12,763
Net loss	(42,208)
Ending balance (in shares) at Jun. 30, 2022 | shares							42,522,397,000		1,000
Ending balance at Jun. 30, 2022	224,585		451,453	(15,487)	(211,849)		$ 440		$ 28
Shares, par value (in GBP per share) | £ / shares						£ 0.008		21,921.504
Beginning balance (in shares) at Mar. 31, 2022 | shares							42,464,566,000		1,000
Beginning balance at Mar. 31, 2022	259,574		448,271	1,647	(190,812)		$ 440		$ 28
Exercise of share options (in shares) | shares							55,727,000
Exercise of share options	4		4
Vesting of restricted stock units (in shares) | shares							2,104,000
Share-based compensation expense	3,178		3,178
Unrealized loss on foreign currency translation	(17,134)			(17,134)
Net loss	(21,037)				(21,037)
Ending balance (in shares) at Jun. 30, 2022 | shares							42,522,397,000		1,000
Ending balance at Jun. 30, 2022	224,585		451,453	(15,487)	(211,849)		$ 440		$ 28
Shares, par value (in GBP per share) | £ / shares						0.008		21,921.504
Shares, par value (in GBP per share) | £ / shares						£ 0.008		£ 21,921.504
Beginning balance (in shares) at Dec. 31, 2022 | shares						42,631,794	42,631,794,000	1	1,000
Beginning balance at Dec. 31, 2022	181,280		458,825	(16,867)	(261,146)		$ 440		$ 28
Exercise of share options (in shares) | shares							3,790,000
Issuance of ordinary shares under ATM offering, net of issuance costs (in shares) | shares							113,420,000
Issuance of ordinary shares under ATM facility, net of issuance costs	1,188		1,187				$ 1
Vesting of restricted stock units (in shares) | shares							30,481,000
Vesting of restricted stock units	0		(1)				$ 1
Shares tendered for withholding taxes	(109)		(109)
Share-based compensation expense	4,071		4,071
Unrealized loss on foreign currency translation	(578)			(578)
Net loss	(24,208)				(24,208)
Ending balance (in shares) at Mar. 31, 2023 | shares							42,779,485,000		1,000
Ending balance at Mar. 31, 2023	161,644		463,973	(17,445)	(285,354)		$ 442		$ 28
Beginning balance (in shares) at Dec. 31, 2022 | shares						42,631,794	42,631,794,000	1	1,000
Beginning balance at Dec. 31, 2022	$ 181,280		458,825	(16,867)	(261,146)		$ 440		$ 28
Exercise of share options (in shares) | shares	128,869					128,869
Vesting of restricted stock units (in shares) | shares						29,220
Net loss	$ (52,543)
Ending balance (in shares) at Jun. 30, 2023 | shares						45,760,250	45,760,250,000	0	0
Ending balance at Jun. 30, 2023	166,396		496,342	(16,728)	(313,689)		$ 471		$ 0
Shares, par value (in GBP per share) | £ / shares						£ 0.008		£ 21,921.504
Beginning balance (in shares) at Mar. 31, 2023 | shares							42,779,485,000		1,000
Beginning balance at Mar. 31, 2023	161,644		463,973	(17,445)	(285,354)		$ 442		$ 28
Exercise of share options (in shares) | shares							125,079,000
Exercise of share options	1	$ 1
Issuance of ordinary shares under ATM offering, net of issuance costs (in shares) | shares							2,824,202,000
Issuance of ordinary shares under ATM facility, net of issuance costs	26,932		26,904				$ 28
Vesting of equity awards under the employee purchase plan (in shares) | shares							23,843,000
Vesting of equity awards under the employee purchase plan	189		189
Cancellation of deferred share (in shares) | shares									(1,000)
Cancellation of deferred share	0		28						$ (28)
Issuance of warrant to purchase ordinary shares	687		687
Vesting of restricted stock units (in shares) | shares							7,641,000
Share-based compensation expense	4,561		4,561
Unrealized loss on foreign currency translation	717			717
Net loss	(28,335)				(28,335)
Ending balance (in shares) at Jun. 30, 2023 | shares						45,760,250	45,760,250,000	0	0
Ending balance at Jun. 30, 2023	$ 166,396		$ 496,342	$ (16,728)	$ (313,689)		$ 471		$ 0
Shares, par value (in GBP per share) | £ / shares						£ 0.008		£ 21,921.504