Annual report pursuant to Section 13 and 15(d)

Share-based compensation - Option Plans (Details)

v3.10.0.1
Share-based compensation - Option Plans (Details)
 1 Months Ended 3 Months Ended 12 Months Ended 46 Months Ended
Jul. 05, 2018
Jun. 22, 2018
Jul. 03, 2017
Nov. 28, 2016
Aug. 11, 2016
Jun. 23, 2016
Mar. 16, 2015
GBP (£)
item
Aug. 31, 2016
director
shares
Dec. 31, 2014
Apr. 30, 2014
Mar. 31, 2014
Dec. 31, 2018
shares
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2009
Apr. 30, 2014
Share based compensation                                  
Maximum value of option grants per participant | £             £ 30,000                    
Scheme limit, grants as a percentage of fully diluted share capital of the Company immediately following the IPO (as a percent)             8.00%                    
Scheme limit, automatic increase percentage (as a percent)             4.00%                    
Number of option schemes | item             3                    
Accelerated vesting (in shares)               361,222                  
Number of non-executive directors | director               2                  
RSU                                  
Share based compensation                                  
Exercise price                       0.001          
Vesting percentage (as a percent)                       25.00%          
Vesting period (in years)                       4 years          
Options granted in March, 2015 and on May 11, 2015                                  
Share based compensation                                  
Contractual term (in years)             10 years                    
Options granted in March, 2015 and on May 11, 2015 | First anniversary                                  
Share based compensation                                  
Vesting percentage (as a percent)                       25.00%          
Options granted in March, 2015 and on May 11, 2015 | Monthly installments over the following three years                                  
Share based compensation                                  
Vesting percentage (as a percent)                       75.00%          
Vesting period (in years)                       3 years          
Options granted in 2009                                  
Share based compensation                                  
Vesting percentage (as a percent)                               100.00%  
Vesting period (in years)                               3 years  
Contractual term (in years)                               10 years  
Options granted in 2011, 2012, 2013, and April 2014                                  
Share based compensation                                  
Contractual term (in years)                   10 years 10 years   10 years 10 years 10 years    
Options granted in 2011, 2012, 2013, and April 2014 | First anniversary                                  
Share based compensation                                  
Vesting percentage (as a percent)                   25.00% 25.00%   25.00% 25.00% 25.00%    
Vesting period (in years)                                 1 year
Options granted in 2011, 2012, 2013, and April 2014 | Annual installments over the following three years                                  
Share based compensation                                  
Vesting percentage (as a percent)                   75.00% 75.00%   75.00% 75.00% 75.00%    
Vesting period (in years)                   3 years 3 years   3 years 3 years 3 years    
Options granted in December 2014                                  
Share based compensation                                  
Contractual term (in years)                 10 years                
Options granted in December 2014 | First anniversary                                  
Share based compensation                                  
Vesting percentage (as a percent)                 25.00%                
Vesting period (in years)                 1 year                
Options granted in December 2014 | Monthly installments over the following three years                                  
Share based compensation                                  
Vesting percentage (as a percent)                 75.00%                
Vesting period (in years)                 3 years                
Non-executive director | Options granted on June 23, 2016 | First anniversary                                  
Share based compensation                                  
Vesting percentage (as a percent)           25.00%                      
Vesting period (in years)           1 year                      
Non-executive director | Options granted on June 23, 2016 | Monthly installments over the following two years                                  
Share based compensation                                  
Vesting percentage (as a percent)           75.00%                      
Vesting period (in years)           2 years                      
Non-executive director | Options granted on August 11, 2016 | First anniversary                                  
Share based compensation                                  
Vesting percentage (as a percent)         100.00%                        
Vesting period (in years)         1 year                        
Non-executive director | Options granted on November 28, 2016 | First anniversary                                  
Share based compensation                                  
Vesting percentage (as a percent)       25.00%                          
Vesting period (in years)       1 year                          
Non-executive director | Options granted on November 28, 2016 | Monthly installments over the following two years                                  
Share based compensation                                  
Vesting percentage (as a percent)       75.00%                          
Vesting period (in years)       2 years                          
Non-executive director | Options granted on July 03, 2017 | First anniversary                                  
Share based compensation                                  
Vesting percentage (as a percent)     100.00%                            
Vesting period (in years)     1 year                            
Non-executive director | Options granted on June 22, 2018 | First anniversary                                  
Share based compensation                                  
Vesting percentage (as a percent)   100.00%                              
Vesting period (in years)   1 year                              
Non-executive director | Options granted in July 05, 2018 | First anniversary                                  
Share based compensation                                  
Vesting percentage (as a percent) 25.00%                                
Vesting period (in years) 1 year                                
Non-executive director | Options granted in July 05, 2018 | Monthly installments over the following two years                                  
Share based compensation                                  
Vesting percentage (as a percent) 75.00%                                
Vesting period (in years)                       2 years