Hamilton was educated at Queen's University, Belfast, and graduated M.B., B.Ch. B.A.O. in 1910. After holding the appointments of senior assistant medical officer at the Portsmouth Infirmary and, two years later, of resident medical officer of the Norwich Workhouse and Infirmary, he returned to Ireland, and joined the R.A.M.C. in March 1915. He entered the war in France on 27th August 1915 with a battalion of the Yorkshire Regiment and was subsequently transferred to the Northampton Regiment. He was promoted to temporary Captain in March 1916. Hamilton was slightly wounded in October 1916 and again fatally wounded on 23rd October by a sniper as he was attending to a wounded man on the front lines. A colleague at the Norwich Infirmary wrote of him as an excellent organiser and possessing marked surgical ability, coupled with a quiet and unassuming manner which made him popular with the staff and governors. Hamilton was the seventh son of the late Mr A Mathewson of Newton-Stewart, co. Tyrone.