Leslie Arnold Hacklett was born in Croydon in 1896, the son of Henry and Constance (née Arnold) Hacklett. He worked for The National Bank.
During the First World War Hacklett left the bank to go on military service. By 1919 he was a Lieutenant in the Communication Squadron, the Royal Air Force, involved in transporting mail and passengers between London and Paris in support of the Versailles Peace Conference. He was accidentally killed while undertaking these duties on 26 February 1919. He was 22 years old.