Joshua was born on 26 October 1908 in Bridgend, Wales to Russian born father Myer, a jewellery dealer, and Manchester born mother Mary and he had two younger sisters Cecilia and Pearl. After the death of Myer in 1927, the family moved to Lambeth in London where Joshua worked as a taxicab driver.

Joshua enlisted at the beginning of the war into the Royal Engineers and was based at Gibraltar Barracks, Aldershot in Hampshire. On the 4 July 1941 he died from a gunshot wound. At the inquest on 7 July 1941, the verdict was that Joshua murdered Harold Tolley and then committed suicide while the balance of his mind was disturbed. Joshua had been charged with a minor breach of discipline of an improper remark and the chief witness was Harold Tolley.