XML 147 R112.htm IDEA: XBRL DOCUMENT v3.21.1
Post-employment benefit plans (Details) - GBP (£)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Disclosure of defined benefit plans [Abstract]      
Unpaid contributions outstanding £ 2,000 £ 1,000  
Total plan expense, current period £ 1,035,000 £ 1,213,000 £ 981,000