John Gilbert was born in October, 1882, and was a New Zealander by birth, the son of Thomas and Ellen Gilbert. He had at least one sibling, a brother, Thomas Gilbert, living at Puheohahu, New Zealand. He enlisted in Melbourne on 9 February, 1915, giving his address as 198 Albert Street, probably a boarding house. On 27 April, he married Mabel Agnes Stormont in Melbourne and. He then changed his next of kin on his enlistment form to his wife, Mrs. Mabel Gilbert, living at 'Morea' Pitt Street, Milson's Point, Sydney. This suggests that she was a Melbourne girl, but that he was living in Sydney and she returned to his address there. He was a clerk by occupation. He trained at Broadmeadows and was taken on strength with the newly raised 22nd Battalion, B Company, sailing to Egypt on 8 May on board HMAT Ulysses A 38. Althoug he was made Private on enlistment, on 4 May, John Gilbert was made Lance Corporal, but then chose to go back to Private.

The 22nd battalion completed their somewhat minimal training  in Egypt and were then sent to the Gallipoli Peninsula as reinforcements. Their first action was to defend established positions to the north of Anzac Cove, relieving another battalion. They stayed at Gallipoli until the withdrawal of ANZAC troops in mid-December, at which time, John Gilbert became ill. Diagnosed with rheumatism (slight) he was placed in the 1st Auxiliary Hospital at Heliopolis on 15 December, probably immediately after disembarkation. From Egypt, he was sent on the HS Karoola to Zeitoun, Italy,  rejoining his unit on 21 December. In Egypt, the 22nd Battalion was placed in the Canal Zone, as part of the defence, before being sent to France.

On 19 March, 1916, the 22nd Battalion left to join the British Expeditionary Force and sail to France. They disembarked at Marseilles on 26 March and went by rail to the Western Front. In April, they saw their first action at Fleurbaix/Fromelles. Then, from 25 July - 7 August, they were in the front line at Pozieres, part of th Battle of the Somme. In that action, the 22nd Battalion was nearly wiped out, losing 27 officers and 656 other ranks. John Gilbert was one of the casualties. He had been promoted to Corporal during the battle, presumably to relace a casualty, but on 11 August was admitted to hospital in France, suffering from shell shock and influenza. His conidiont must have been serious, because he was sent back to England from Calais on 1 September and placed in the 4th General Hospital at Denmark Hill. He was discharged on 16 October, 1916 and from there, he went to Southampton, where embarked on the HS Hororata on 25 October to return home. He was discharged from the AIF on 13 April, 1917.

It is difficult to follow him from there.  In 1930, according to the Electoral Rolls, he and Mabel were living in Cabramatta Rd., Cabramatta, NSW. She was working as a grocer, he was listed as a dealer. In 1933, they were in Hemphill Rd., Liverpool. He was then a grocer, while Mabel was listed as Home Duties. They probably had their son by then, and perhaps other children. In 1935, they were still in Hemphill Rd., but after that, it is impossible to trace them in the Electoral Roll. In 1967, their son, P.J. Gilbert wrote to the army authorities on behalf of his mother, by then a widow, applying for a Gallipoli medal.