 After starting his career in Burma, Garthwaite served in senior posts with the British Forestry Commission from 1947 to 1970, and was then made president of the Royal Society of Forestry of England, Wales and Northern Ireland from 1972 to 1974.He was a silviculturalist who had an extensive knowledge of trees and forestry practice, but he also recognised the advantages of different silvicultural practices in different circumstances.Garthwaite was born at Guisborough, in North Yorkshire, on 22 October 1909.