Annual report pursuant to Section 13 and 15(d)

Share based compensation - Option Activity (Details)

v3.10.0.1
Share based compensation - Option Activity (Details)
$ in Thousands
12 Months Ended
Dec. 31, 2018
£ / shares
shares
Dec. 31, 2017
£ / shares
shares
Dec. 31, 2016
shares
Dec. 31, 2018
USD ($)
shares
Options        
Outstanding at the beginning of the period (in shares) | shares 74,943,667      
Granted (in shares) | shares 20,771,970 29,924,787 19,404,373  
Exercised (in shares) | shares (5,334,936) (1,142,904) (63,192)  
Forfeited (in shares) | shares (2,815,982)      
Outstanding at the end of the period (in shares) | shares 87,564,719 74,943,667    
Weighted Average Exercise Price Per Option        
Outstanding at the beginning of the period (in dollars per share) | £ / shares £ 0.58      
Granted (in dollars per share) | £ / shares 0.63      
Exercise price | £ / shares 0.42      
Forfeited (in dollars per share) | £ / shares 0.80      
Outstanding at the end of the period (in dollars per share) | £ / shares £ 0.60 £ 0.58    
Additional disclosures        
Outstanding - Average Remaining Contractual Term (Years) 7 years 7 months 6 days      
Outstanding - Aggregate Intrinsic Value | $       $ 25,905
Exercisable - Options | shares       47,678,481
Exercisable - Weighted Average Exercise Price Per Option | £ / shares £ 0.55      
Exercisable - Average Remaining Contractual Term (Years) 6 years 8 months 12 days      
Exercisable - Aggregate Intrinsic Value | $       $ 15,207