Income Taxes - Schedule of Income Tax Expense Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income taxes at UK statutory rate	$ (17,309)	$ (13,592)	$ (11,458)
Permanent differences	14	69	340
UK R&D tax credit	5,423	3,747	1,664
Change in valuation allowance	15,038	29,180	8,683
State income taxes	10	1	(5)
Deferred tax asset true-up	8	80	919
Return to Provision	1,580	(854)	0
Equity Compensation	(782)	(8,302)	0
Change in UK Tax Rate	(3,609)	(10,147)	0
Other	35	17	(111)
Total provision for income taxes	$ 408	$ 199	$ 32

Effective Income Tax Rate Reconciliation, Deferred Tax Asset Reconciliation, Amount

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Effective Income Tax Rate Reconciliation, Permanent Differences, Amount

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Amount of difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operation, attributable to expense for award under share-based payment arrangement. Excludes expense determined to be nondeductible upon grant or after for award under share-based payment arrangement.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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