John was born on 7 August 1897 in Balbriggann (Balrothery), Dublin, Ireland, to Patrick and Catherine (née Harford). He joined an elder brother Thomas (1896) and was joined later by 2 younger sisters Mary (1906) and Eileen (1909) thus completing the family unit.

He joined the Royal Navy on 23 November 1912 when he travelled to Devonport and crossed the gangway of the “Boy Training Ship” HMS IMPREGNABLE and signed on as a Boy Second Class. On 8 March 1913 he was drafted to HMS GANGES at Shotley, Suffolk, where on 23 June he was selected for the communications branch and became “Sig Boy” with a draft on 14 November to HMS VIVID 1, the Royal Naval Barracks in Devonport. On 29 November he had a draft to HMS LION for 14 months with a 1 month break on HMS PRINCESS ROYAL before returning to LION on 26 February 1915. He was advanced to Ordinary Signalman 13 May and rated up to Signalman on 19 August 1916 and while on board volunteered for the submarine service, which he entered with a draft to HMS DOLPHIN in Portsmouth on 14 October 1916. With the introductory course completed he was drafted to HMS MAIDSTONE based in Harwich for HMS E50 on 16 March 1917.

E50 departed Harwich on 21 January 1918 for a patrol area off the West coast of Denmark and was not seen or heard from again until 2011. Initial reports thought that she had struck a mine on route to the desigated patrol area on the seaward side of 54.4N, 6.15E. The date recorded for loss is 1 February 1918 as this is the date the vessel was declared “missing, presumed lost”.

In 2011 an authorised Danish diving expedition found the wreck of an E-class submarine 65Nm West of the Danish coastal town of Nymindegab. This proved to be the long lost E50. She was sat on the sea floor, her planes set to rise with no apparent damage to her hull except where her conning tower had been ripped off by fishing trawler activity. To save further damage the tower was recovered, cleaned then preserved and is now in the “Jutland Memorial Museum” in the town of Thyboran, Denmark.

Signalman John Joseph Mulhall,  Svc No. J21302 “Crossed The Bar” sometime in late January 1918 in company with the other 30 of his shipmates. He is commemorated on the Plymouth Naval Memorial on Panel 27.