Consolidated Statements of Shareholders’ Equity (Deficit) $ 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 (LOSS)/ INCOME USD ($)	ACCUMULATED DEFICIT USD ($)	CONVERTIBLE PREFERRED SHARES USD ($) shares	A CONVERTIBLE PREFERRED SHARES USD ($) shares	B CONVERTIBLE PREFERRED SHARES USD ($) shares	ORDINARY SHARES £ / shares shares	ORDINARY SHARES 2021 Award shares	ORDINARY SHARES 2020 Award shares	ORDINARY SHARES COMMON STOCK USD ($) 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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Convertible preferred shares outstanding (in shares) | shares	9,782,505								2,650,980	7,131,525	0
Common stock, par value (in GBP per share) | £ / shares												£ 0.008						£ 21,921.504
Convertible preferred shares beginning balance at Dec. 31, 2019									$ 3,761	$ 35,147	$ 0
Beginning balance (in shares) at Dec. 31, 2019 | shares															10,752,429				0
Beginning balance at Dec. 31, 2019	$ (30,390)			$ 7,162			$ (98)	$ (37,565)							$ 111				$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of B convertible preferred shares, net of issuance costs (in shares) | shares											4,913,404
Issuance of B convertible preferred shares, net of issuance costs											$ 61,316
Conversion of notes into B convertible preferred shares (in shares) | shares											1,723,263
Conversion of notes into B convertible preferred shares											$ 21,614
Exercise of share options (in shares) | shares															197,702
Exercise of share options	0			(2)											$ 2
Exercise of share options but shares not issued	16			16
Forfeiture of ordinary shares (in shares) | shares															(63,972)
Forfeiture of ordinary shares	0			(1)											$ (1)
Effect of corporate reorganization including conversion of preferred shares to ordinary shares (in shares) | shares									(2,650,980)	(7,131,525)	(6,636,667)	(16,419,172)			(16,419,172)				(1)
Effect of corporate reorganization including conversion of preferred shares to ordinary shares	(121,838)			(121,643)					$ (3,761)	$ (35,147)	$ (82,930)				$ (167)				$ (28)
Issuance of ordinary shares, net of issuance costs (in shares) | shares															8,625,000
Issuance of ordinary shares, net of issuance costs	132,765			132,677											$ 88
Share-based compensation expense	17,983			17,983
Unrealized gain (loss) on foreign currency translation	14,683						14,683
Net loss	(60,334)							(60,334)
Ending balance (in shares) at Dec. 31, 2020 | shares															35,930,331				1
Ending balance at Dec. 31, 2020	$ 196,561			279,480			14,585	(97,899)							$ 367				$ 28
Convertible preferred shares ending balance (in shares) at Dec. 31, 2020 | shares									0	0	0
Convertible preferred shares ending balance at Dec. 31, 2020									$ 0	$ 0	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Convertible preferred shares outstanding (in shares) | shares									0	0	0
Common stock, par value (in GBP per share) | £ / shares												£ 0.008						£ 21,921.504
Exercise of share options (in shares) | shares	1,244,709												1,476,936	232,227		1,244,709	232,227
Exercise of share options		$ 1,905	$ 0		$ 1,891	$ (3)										$ 14	$ 3
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
Issuance of ordinary shares to settle vested restricted stock units (in shares) | shares															12,607
Share-based compensation expense	8,639			8,639
Unrealized gain (loss) on foreign currency translation	(5,745)						(5,745)
Net loss	(71,742)							(71,742)
Ending balance (in shares) at Dec. 31, 2021 | shares												42,019,874			42,019,874			1	1
Ending balance at Dec. 31, 2021	$ 284,412			444,750			8,840	(169,641)							$ 435				$ 28
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock, par value (in GBP per share) | £ / shares												£ 0.008						£ 21,921.504
Exercise of share options (in shares) | shares	462,722											462,722			462,722
Exercise of share options	$ 401			397											$ 4
Issuance of ordinary shares, net of issuance costs (in shares) | shares															44,416
Issuance of ordinary shares, net of issuance costs	440			439											$ 1
Issuance of ordinary shares to settle vested restricted stock units (in shares) | shares												82,622			82,622
Issuance of ordinary shares under 2020 employee share purchase plan (in shares) | shares																	22,160
Issuance of ordinary shares under 2020 employee share purchase plan			$ 199			$ 199
Shares tendered for withholding taxes	(83)			(83)
Share-based compensation expense	13,123			13,123
Unrealized gain (loss) on foreign currency translation	(25,707)						(25,707)
Net loss	(91,505)							(91,505)
Ending balance (in shares) at Dec. 31, 2022 | shares												42,631,794			42,631,794			1	1
Ending balance at Dec. 31, 2022	$ 181,280			$ 458,825			$ (16,867)	$ (261,146)							$ 440				$ 28
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock, par value (in GBP per share) | £ / shares												£ 0.008						£ 21,921.504