Robert C.G. Clark was educated at the Technical College, London, and was an associate of the (British) Institution of Electrical Engineers. He came to South Africa in December 1896 and became a member of the South African Society of Electrical Engineers, which flourished briefly in Johannesburg from 1897 to 1899. At their meeting in January 1898 he read a paper on "Interior wiring", and in June 1899 another on "Direct coupled versus belt-driven sets".
Clark served as a trooper in the First Imperial Light Horse during the Anglo-Boer War, from September 1899 to February 1901, and rose to the rank of captain in the Imperial Light Horse Volunteers. One of his hobbies was rifle-shooting, and in 1904 he set a world record in a rifle-shooting competition in Johannesburg.