[2][3] On returning to England in 1893 he rejoined Bryan Donkin & Company as a draughtsman, later becoming assistant to the manager.
A cousin, William Frederick Donkin, had been a famed climber and secretary of the Alpine Club who died on a climb in the Caucasus in 1888.
He soon became an enthusiast and climbed many of the Alpine peaks including Matterhorn, Monte Rosa, Zinalrothorn, Dent Blanche and the Dom as well as several mountains of North Wales.
Donkin worked heavily in hydro-electric power and was involved in several large scale projects.
He acted as an adviser to the government on a proposed Severn barrage scheme,[2] and was personally responsible for the crucial technical appendices of the report (HMSO 1945).
[4] He assisted the Ministry of Labour in their preparations for the Second World War by volunteering his services as chairman of the engineering section of the National Register of Scientists, Technical Experts and Professional Men which was established to allow the government to better use the skills of these men for the war effort.
[4] In the 1930s he became interested in uses for the heated water generated by power stations and this was the subject of his presidential address to the Institution of Civil Engineers in 1937.
After the war he devised a way of using it to heat homes and businesses which was put into use on a housing estate in Pimlico.