Leon was born on 4 August 1913 in Fulham, London with the name Leonard Cohen. His father Charles, who worked as a tailor, was born in Russia and his mother Rose nee Granard was German born.

Leon was well known as a sportsman and a body builder and before joining the Army was a boxing coach to Lime Grove A.R.P. depot. He enjoyed sculling and played badminton and on joining the Army he trained as a physical training instructor. He met Leah Zafer who was also a physical culturist, first class swimmer and a talented musician. They married in July 1940 only three months before his death and lived at 8 Addison Road in Chiswick.

Leon was killed on 7 October 1940 in Watford, Hertfordshire and his death certificate states that his death was due to war operations.