Quarterly report pursuant to Section 13 or 15(d)

Share-based compensation - Options (Details)

v3.10.0.1
Share-based compensation - Options (Details)
3 Months Ended 9 Months Ended
Sep. 30, 2018
$ / shares
shares
Sep. 30, 2017
$ / shares
shares
Sep. 30, 2018
$ / shares
shares
Sep. 30, 2018
£ / shares
shares
Sep. 30, 2017
$ / shares
shares
Number of options granted (in shares) | shares 757,273 8,756,211 12,187,614 12,187,614 28,959,363
Weighted average fair value (in dollars per share) | $ / shares $ 1.09 $ 0.34 $ 0.82   $ 0.34
RSU          
Number of options granted (in shares) | shares 1,259,760   7,966,716 7,966,716  
Weighted average fair value (in dollars per share) | $ / shares $ 1.67   $ 1.40    
Exercise price | £ / shares       £ 0.001  
Vesting period (in years)     4 years 4 years  
Contractual term (in years)     10 years 10 years  
First anniversary | RSU          
Vesting percentage (as a percent)     25.00% 25.00%  
Annual installments over the following three years | RSU          
Vesting percentage (as a percent)     75.00% 75.00%