Leon was born in Dumbarton 1877. His father was William Denny, a shipbuilder who died in 1887. His mother was Lelia Mathilda Denny (née Serena. Her father was Italian, mother was Belgian) who re-married in April 1889, to Sir Bernard Samuelson 1st Bt. Leon was educated at Clifton College. He moved to London and became a Lloyds underwriter. He was commissioned into the 3rd Battalion Queen’s Royal West Surrey Regiment (Militia) on 10 Feb 1897 and then joined the King’s Dragoon Guards as a 2nd Lieutenant 4 Jan 1899. Lieutenant 22 Nov 1899. He went with the regiment to South Africa and was wounded at Ventersburg on 29 Mar 1901. He was appointed Signalling Officer in South Africa 1902. Promoted to captain in 1905 but resigned on 21 April 1906 and went on the Reserve of officers.
Leon was an excellent amateur jockey, his greatest win was on 2 Mar 1906 at Sandown Park when he came first in the Grand military Gold riding Royal Blaze. Before the war he lived at 20 Ladbroke Gardens, Kensington, and when the war began he was mobilised and posted to France on 23 Oct 1914. He was killed in action at Robecque, on 13 May 1915 aged 38, and commemorated at Ypres (Menin Gate) Memorial. His mother died a month later on 18 June 1915 (the centenary of the Battle of Waterloo). She had volunteered in the Voluntary Aid Detachment but contracted a disease while on duty and died in Hospital at Rouen.
