87 Squadron flying Sopwith Dolphins, and was awarded the Distinguished Flying Cross in October 1918, having destroyed four enemy aircraft. His final total was 11 confirmed victories. 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.
Leslie flew with 87 Squadron using Sopwith Dolphins and was recognized with the Distinguished Flying Cross in October 1918 after destroying four enemy planes. His total number of confirmed victories reached 11. Both of his siblings also participated in the war: Charles received military honors for bravery, while Phyllis joined the Royal Air Force.