Leonard was born in Wolverhampton in 1894, the son of Thomas and Catherine Frost. In 1901 they were living at 8 Owen Road, Wolverhampton, along with Leonard’s siblings Allyn Walker, Willfrid Earnest [sic], Dorothy, Enid Florence and Ethel Elsie. By 1911 they were at 62 Merridale Road, Wolverhampton, with an additional sibling, Frederick Harry. Leonard was an apprentice wood engraver.
In September 1915, he enlisted with the Royal Army Medical Corps. However, he suffered with trench fever and was sent home with it on two occasions. He survived to the end of the war, but suffered from asthma as a result. In 1921, he contracted influenza, and died on 13 November 1921 at his home at 21 Chapel Ash, Wolverhampton. His family were satisfied that he died of natural causes and did not wish for a postmortem. The coroner’s inquest found that he had died of natural causes, although his name still appears on the Wolverhampton Roll of Honour.