Errol Cappie Nepean Devlin was born at Penrith, New South Wales during 1891 to parents Sidney William and Mary. A clerk by trade, he first enlisted at Liverpool on 12 August 1914 at the age of 23 with the Australian Naval and Military Expeditionary Force (ANMEF), Tropical Unit, 1st Battalion. He left Australia aboard HMAT Berrima on 19 August 1914 and served with the ANMEF to capture German assets in New Guinea.

After returning to Australia, he chose to enlist once again. On 22 March 1915 he again enlisted at Liverpool and was assigned to the 18th Infantry Battalion with the rank of private. Devlin departed Sydney aboard HMAT Ceramic on 25 June 1915. He served with the 18th Battalion at Gallipoli and on the Western Front until he was killed in action on 30 May 1916 in France. He was 25 years old. Errol Devlin is buried at Brewery Orchard Cemetery, Bois-Grenier, France.