[1] At the outbreak of the war in 1914, Hollinghurst enlisted with the Royal Engineers[2] participating in the Gallipoli landings and was wounded at Salonika.

In 1916 he was commissioned into the 3rd Battalion, the Middlesex Regiment, and later in the same year was seconded to the Royal Flying Corps (RFC).

Leslie's two siblings also served in the war: Charles Stanley Hollinghurst was also in the RFC and was awarded the Military Cross and Distinguished Conduct Medal, while Phyllis Hollinghurst enlisted in the Royal Air Force; the Women's Royal Air Force.

38 group were later involved in Operation Market Garden, for which Hollinghurst was awarded United States Distinguished Flying Cross.

[3] Hollinghurst died on 8 June 1971, having collapsed on his journey back from a commemoration of the Normandy Landings.