On 23 may 1896, Rex Leah was born in the Levenshulme area of Manchester, the only son of Sidney and Hester Leah. He had a sister, Edith, who was 5 years older. At the time of the 1901 Census, the family was living at 4 Clarendon Avenue, Heaton Moor but later moved to 15 Cavendish Road, Heaton Mersey. Sidney was educated at Stockport Technical School and, later, worked as a Life Insurance Clerk. His employer was probably the Co-operative Wholesale Society which lists a W R Leah amongst its employees who served (Page 470, Manchester City Battalions Book of Honour)
Rex joined the army on 26 September 1914, enlisting as a private (service number 2610) in the 2/7th Battalion, Manchester Regiment. His enlistment papers show him to be five feet five inches tall with a 35 inch chest. Whilst in training at Southport he was promoted to Lance Corporal, on 1 May 1915 and awarded the "crossed flags" for signalling (this was a proficiency badge which he would have worn on his uniform sleeve). In May 1915, the Battalion moved to Crowborough for further training. As with many middle class young men, Rex was selected to train to become an officer and he transferred to the Inns of Court Officer Training Corps at Berkhampstead, on 11 September 1915. He later attended Officer Cadet School at the Curragh in Ireland, where he was appointed as a signalling instructor.
He was commissioned into the 1/4th Battalion of the King's Own on 17 July 1916. It has not been possible to discover any further information about Rex, except that it is known he was killed in action. Unusually, there is no reference to him in the Regimental History, nor in the Battalion's own War Diary, written at the time. Ovillers Cemetery is some distance from the part of the Somme battlefield where the 1/4th Battalion was on 10 September and the most likely explanation is that Rex had been temporarily assigned to another unknown unit and was with it when he was killed.
Rex's sister, Edith, is known to have served as a Red Cross nurse, being attached to the Heaton Moor and Heaton Mersey Division.