John (Jack) Marchant Sellar was born in Richmond in 1897. His parents were George Smythe (d. 1919) and Josephine Sellar. When he enlisted on 15 January 1916 Jack was 18 years and 5 months.. He gave his occupation as salesman and stated that he had been a member of the senior cadets, area 64 East Melbourne for four years, and a member of the citizens' cadets, 64th Infantry, Melbourne for six months. He gave his father as his next of kin who was then living at 21 Grey street, East Melbourne. This had been the family home from at least 1909. After temporary placements with other battalions at Broadeadows he was appointed to the 2nd Pioneer Battalion, 4th Reinforcements at Seymour.
He embarked on 28 July 1916 on the Themistocles and arrived at Plymouth on 11 September 1916. He joined his unit in France on 24 November 1916. He was wounded in action with a shell wound to the shoulder on 9 June 1918 and was hospitalised. After rejoining his unit on 18 June 1918 he was again wounded in action 17 July 1918, this time by gassing. He rejoined his battalion on 10 Ausut 1918. He was tansferred to England later in the year and early in 1919 spent some time ni hospital with flu. He embarked for return to Australia on 3 May 1919 and was discharged on 5 August 1919.
Little is known of his life after the war. He was living at 1 Mary Street, Hawthorn in 1926 when he wrote to claim his medals. He died at Beaumaris on 19 June 1965.