Warrant liability	12 Months Ended
Dec. 31, 2020
Warrant liability
Warrant liability	8. Warrant liability In 2017, the Company issued 200,000 warrants to subscribe for Series A Preferred Shares, at £0.01 each. In conjunction with the completion of the IPO, 120,000 warrants to subscribe for Series A Preferred Shares were exercised for 171,480 ordinary shares. The remaining 80,000 warrants, which were exercisable into 114,320 ordinary shares following the completion of the IPO, as adjusted for the impact of the Share Capital Reorganization (Note 7), were exercised in 2019 and 2020. In addition, in 2017, the Company issued a total of 743,287 warrants to subscribe for Series B1 Preferred Shares, with an exercise price of £0.01, in conjunction with the issuance of 3,947,198 Series B1 Preferred Shares. On March 7, 2019, the holders of the warrants to subscribe for Series B1 Preferred Shares agreed that 50% of the warrants would be exercised in conjunction with the IPO and 50% of the warrants would expire. The modification resulted in an incremental change in fair value of $0.1 million, which is included in other expense for the year ended December 31, 2019. On May 28, 2019, in conjunction with the completion of the IPO, all Series B1 Preferred share warrants were exercised for 531,077 ordinary shares, as adjusted for the impact of the Share Capital Reorganization (Note 7). Prior to the completion of the IPO, the warrants to subscribe for Series A and Series B1 Preferred Shares were recorded as a liability and remeasured to fair value at each reporting date. Changes in the fair value of the warrant liability were recognized as other expense, net in the consolidated statements of operations and comprehensive loss. Upon the closing of the IPO on May 28, 2019, warrants that were not exercised in conjunction with the IPO automatically became warrants to subscribe for ordinary shares, and meet the criteria to be classified as shareholders’ equity (deficit). As such, following the final remeasurement on May 28, 2019, the Company reclassified the carrying value of the warrant liability to additional paid-in-capital in the consolidated balance sheet.

8. Warrant liability

In 2017, the Company issued 200,000 warrants to subscribe for Series A Preferred Shares, at £0.01 each. In conjunction with the completion of the IPO, 120,000 warrants to subscribe for Series A Preferred Shares were exercised for 171,480 ordinary shares. The remaining 80,000 warrants, which were exercisable into 114,320 ordinary shares following the completion of the IPO, as adjusted for the impact of the Share Capital Reorganization (Note 7), were exercised in 2019 and 2020.

In addition, in 2017, the Company issued a total of 743,287 warrants to subscribe for Series B1 Preferred Shares, with an exercise price of £0.01, in conjunction with the issuance of 3,947,198 Series B1 Preferred Shares.

On March 7, 2019, the holders of the warrants to subscribe for Series B1 Preferred Shares agreed that 50% of the warrants would be exercised in conjunction with the IPO and 50% of the warrants would expire. The modification resulted in an incremental change in fair value of $0.1 million, which is included in other expense for the year ended December 31, 2019. On May 28, 2019, in conjunction with the completion of the IPO, all Series B1 Preferred share warrants were exercised for 531,077 ordinary shares, as adjusted for the impact of the Share Capital Reorganization (Note 7).

Prior to the completion of the IPO, the warrants to subscribe for Series A and Series B1 Preferred Shares were recorded as a liability and remeasured to fair value at each reporting date. Changes in the fair value of the warrant liability were recognized as other expense, net in the consolidated statements of operations and comprehensive loss. Upon the closing of the IPO on May 28, 2019, warrants that were not exercised in conjunction with the IPO automatically became warrants to subscribe for ordinary shares, and meet the criteria to be classified as shareholders’ equity (deficit). As such, following the final remeasurement on May 28, 2019, the Company reclassified the carrying value of the warrant liability to additional paid-in-capital in the consolidated balance sheet.