Staff numbers and costs

12 Months Ended

Dec. 31, 2020

4.	Staff numbers and costs

The average number of persons employed by the Group (including the Board) during the year, analyzed by category, was as follows:

	2020 No. of employees		2019 No. of employees		2018 No. of employees
Research		177		284		299
Development		96		108		95
Corporate		56		67		67
Total		329		459		461

The aggregate staff costs of these persons were as follows:

	2020 £’000		2019 £’000		2018 £’000
Wages and salaries		29,038		31,920		29,501
Social security costs		2,131		2,767		2,731
Share-based payments (Note 25)		8,162		3,056		666
Contributions to defined contribution plans (Note 27)		1,035		1,213		981
		40,366		38,956		33,879

During the year ended December 31, 2020, the Group undertook a corporate restructure incurring costs of £1.2 million. The restructure was completed in the second quarter of 2020 and reduced the overall headcount, at that time, by 78 employees