Leonard Richardson was born on 5 June 1889, fifth son of the late Sir Thomas Richardson, formerly Unionist Member of Parliament for the Hartlepools, and Lady Constance Richardson of The Grange, Kirklevington, Yorkshire. Educated at Rossall School, he entered the Royal Navy in May 1904, later serving as a Midshipman in HMS HAMPSHIRE.
He was promoted to Sub Lieutenant in January 1909 serving in HMS VENERABLE until his promotion to Lieutenant in October 1911. He was appointed to HMS ARROGANT ‘..for training in submarines’ in January 1912 and was one of four officers under training who died when HMS A3 was lost with all hands. He is buried in Haslar Cemetery.