Leslie was born near Armidale NSW to Alexander and Ellen Faint. He was the eldest child in their family. At the age of twenty two he enlisted in January 1916 at Armidale, giving his occupation as Farmer and stating that he had served six years with the 5th Light Horse.
After joining the 33rd Battalion B Company he was appointed Sergeant, and left Australia in May on HMAT A74 Marathon. Nine weeks later his Battalion arrived in England where further training commenced at Salisbury Plain until he was sent to France in November. During the Battle of Messines Leslie was one of the many wounded. The following year he became a 2nd Lieutenant. During April 1918 he was gassed and transferred to England for treatment, returning to France after four months. Just two weeks later Leslie was wounded and again returned to England where he was hospitalised with a gunshot wound to his leg.
During October 1918 Leslie was recommended for the award of the Military Cross for ‘conspicuous gallantry and devotion to duty near Bray … He showed initiative and judgement and led his men unflinchingly through intense fire until he was wounded’. This award was granted in 1919. (Commonwealth Gazette No 67 3 June 1919) About this time he became a Commissioned Lieutenant in the British Army.
Before leaving England in 1919 Leslie was given leave to ‘undergo a course of instruction in Wool Handling and General Agriculture at Bradford Technical College’ in England. Six years after his return to Australia Leslie married Gladys Turner of Inverell, a sister of Frank and Ernest Turner who also served during the War.
Leslie and his wife lived on a farming and grazing property at Dinton Vale north of Inverell during the 1930s, later moving to Inverell where he died in 1977. Several of Leslie’s descendants live in the Inverell district.