 He studied at evening classes, eventually becoming a student of Glasgow University and graduating BSc in 1911.He then became a post graduate researcher, gaining a doctorate (DSc) in 1916 in the chemistry of radioactive substances.He was associated with the Beatson Oncology Centre where he studied the effects of radium on cancerous growths at the beginning of World War I.

Fleck was appointed to the board of ICI in 1944 and was its chairman from 1953 to 1960.