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Exchange rates in US$
12 Months Ended
Dec. 31, 2020
Foreign exchange rates [abstract]  
Exchange rates in US$
40 Exchange rates in US$
The principal exchange rates used in the preparation of the 2020 financial statements were:
Full-year averageYear-end
202020192018202020192018
Sterling
1.28 1.28 1.34 1.36 1.31 1.27 
Australian dollar
0.69 0.70 0.75 0.77 0.70 0.70 
Canadian dollar
0.75 0.75 0.77 0.78 0.77 0.73 
Euro
1.14 1.12 1.18 1.23 1.12 1.14 
South African rand
0.061 0.069 0.076 0.068 0.071 0.069