Income taxes (Tables)

12 Months Ended

Dec. 31, 2021

Income taxes

Schedule of loss before income tax expenses

Loss before income tax expense is as follows (in thousands):

	Year ended		Year ended		Year ended
	December 31,		December 31,		December 31,
	2021		2020		2019
U.S.	$	1,625	$	(1,359)	$	(494)
U.K.		(158,924)		(128,571)		(136,429)
Loss before income tax expense	$	(157,299)	$	(129,930)	$	(136,923)

Schedule of components of income tax expense

The components of income tax expense are as follows (in thousands):

	Year ended		Year ended		Year ended
	December 31,		December 31,		December 31,
	2021		2020		2019
United States:
Federal	$	791	$	162	$	242
State and local		—		—		—
U.K.		—		—		—
Total current tax expense		791		162		242
United States:
Federal		—		—		—
State and local		—		—		—
U.K.		—		—		—
Total deferred tax expense		—		—		—
Total income tax expense	$	791	$	162	$	242

Schedule of deferred tax assets and liabilities

As of December 31, 2021 and 2020 the tax effects of temporary differences and carryforwards that give rise to deferred tax assets and liabilities were as follows (in thousands):

	December 31,		December 31,
	2021		2020
Deferred tax liabilities
Property, plant and equipment:	$	(922)	$	(796)
Operating lease right-of-use assets		(1,757)		(2,009)
Other		(238)		(156)
Total		(2,917)		(2,961)
Deferred tax assets
Share-based compensation expense		15,584		9,292
Intangibles		2,401		1,745
Operating lease liabilities		2,143		2,343
Net operating loss and expenditure credit carryforwards		114,972		71,742
Other		260		237
Total		135,360		85,359
Valuation allowance		(132,443)		(82,398)
		2,917		2,961
Net deferred tax asset/(liability)	$	—	$	—

Schedule of movements in deferred tax asset valuation allowance

The movements in the deferred tax asset valuation allowance for the year ended December 31, 2021 and 2020 are as follows (thousands):

	2021		2020
Valuation allowance at January 1,	$	82,398	$	59,172
Increase in valuation allowance through net loss		50,046		23,025
Increase/(decrease) in valuation allowance through other comprehensive loss		1,512		(2,696)
Foreign exchange translation adjustments		(1,513)		2,897
	$	132,443	$	82,398

Schedule of the effective tax rate reconciliation

Reconciliation of the U.K. statutory income tax rate to the Company's effective tax rate is as follows (in percentages):

	Year ended		Year ended		Year ended
	December 31,		December 31,		December 31,
	2021		2020		2019
U.K. tax rate	19.0	%	19.0	%	19.0	%
Tax-exempt reimbursable tax credits included within pretax Research and development expense	4.1	%	2.8	%	2.8	%
Surrender of R&D expenditures for R&D tax credit refund	(10.3)	%	(8.4)	%	(7.7)	%
Expenses not deductible	(0.2)	%	(1.4)	%	—	%
Permanent differences for unrealized foreign exchange on intercompany loans of a long-term investment nature	—	%	—	%	(1.5)	%
Change in valuation allowances	(31.8)	%	(17.8)	%	(12.4)	%
Change in tax rates	18.1	%	4.1	%	—	%
Difference in tax rates	—	%	—	%	(1.2)	%
R&D tax credits generated	2.0	%	1.8	%	1.5	%
Other	(1.4)	%	(0.1)	%	(0.7)	%
Effective income tax rate	(0.5)	%	(0.0)	%	(0.2)	%