Hugh studied at Trinity College, taking his M.B., B.Ch in 1904. He joined the R.A.M.C. on 31st July 1905 at the rank of Lieutenant, then saw service in India from 1908 to 1913. During this time he was promoted to Captain on 31st January 1909. Hugh entered the war in France on 20th August 1914, attached to the 10th Field Ambulance. He gained promotion to Major on 15th October 1915, but served under the rank of temporary Lieutenant Colonel from 9th November the same year. He was killed whilst serving with the 94th Field Ambulance. He met his death while evacuating the wounded from an advanced dressing station of which he was in charge. His commanding officer wrote of Hugh's efficiency and sympathetic nature, in which the latter endeared him to the men and the former evident in his words: "I was about to appoint him to command - casualty clearing station. I recently inspected his field ambulance, and came away so refreshed, feeling that I had just seen something really efficient." Hugh was the elder son of Captain Hugh Stewart of Kilkenny, and the grandson on Sir Hugh Stewart, Bart; and the husband of Muriel Dalzell Stewart of 4 Rostrevor Terrace, Ratligar, Dublin - married in 1907, they had three children.