Frederick Jenkyn had two lives as a volunteer and gave 874 days of service to Australia in World War 1. He first enlisted on 16 July, 1915, and gave his occupation as Hospital Assistant. He was at that time 30 years and eleven months old, single, with his next of kin his father, living in East Melbourne. Because of his experience, he was placed in the Australian Army Medical Corps (AAMC) and sent to work at the No 5. Australian General Hospital in St Kilda Rd., Melbourne. He stayed there for almost a year and was then discharged at his own request, finishing his service on 16 June, 1916.

He enlisted again on 9 May 1917, giving his occupation as Cyanidist, the term used for rabbit exterminators, who generally moved from farm to farm to eradicate the pest. He was sent  to Broadmeadows for 12 days training and was then moved to Bendigo and placed with the AMC there for a month, before embarkijng from Melbourne on HMAT Nestor on 21 November, 1917, and disembarking first at Suez on 15 December, then at Southampton on 24 January, 1918. From here, he went to Parkhouse, though wehther for training or to help with wounded soldiers is not recorded. On 2 April, 1918, he was sent to France, marching in on 6 Arpril to the 2nd Australian General Hospital at Wimereux, on the Somme. He stayed with the 2nd AGH until 20 November, 1919.

On his return, he stayed with his father at 125A George St., East Melbourne. By 1923, he married Violet Maud Penhall. They lived at 632 Elizabth St, Carlton South, and he worked as a storeman. On 6 November, 1924, the Vitorian Police Gazette had a notice of stolen property: Frederick Jenkyn, Teddington Rd., Hampton, reports stolen from his dwelling an 18 ct. gold Elgin watch, with a monogram G.J. on the back. Value: 20 pounds. In 1937, the couple were at 35 Palmer St, Fitzroy. 

At some stage, the couple moved to NSW. In 1966, a notification was sent to Base Rceords, Melbourne, saying that Frederick Jenkyn had died at the Graythwaite Hospital, Ryde.