Born on 28 June 1917 in Nongoma, Natal Province, South Africa, Nettleton was the grandson of Admiral A.T.D. Nettleton. He was educated at Western Province Preparatory School in Cape Town from 1928 to 1930. Nettleton served as a naval cadet on the General Botha training ship, and then for 18 months in the South African Merchant Marine. He took up civil engineering, working in various parts of South Africa.
