He was born in Wonthaggi to Anglican minister Karl E. Hamilton and Alice Marion Trewartha.
He was educated at Maffra, Orbost and Caulfield Grammar School, before studying at the University of Melbourne, graduating with a Bachelor of Commerce in 1948.
From 1944 he served with the 2/3rd Pioneer Battalion in the Middle East and New Guinea, winning promotion to major, being mentioned in dispatches, and being awarded the Efficiency Decoration.
After the war he remained in the Citizen Military Forces until 1968, achieving the rank of colonel.
In 1967 he won a by-election for the Victorian Legislative Council seat of Higinbotham, representing the Liberal Party.