Leonard was born in Wolverhampton in 1896, the son of James and Celeste Lawson. In 1901 and again in 1911, he was living with his parents at 17 Merridale Lane, along with his siblings James Harold and Robert Louis. He attended Wolverhampton Grammar School.
By 5 September 1914, his address was 65 Finchfield Road, Wolverhampton, as his name was amongst a list of men “willing to join” the special service companies, printed in the Midland Counties Express. His name also appeared in the Express & Star on 30 October 1914, as one of the local men who had enlisted with one of the non-manual companies. He enlisted with the 6th Battalion of the South Staffordshire Regiment (number 3011), first serving in France on 5 March 1915. He was unfortunately killed in action on 13 October 1915, and is commemorated on the Loos Memorial.