Ralph Mortiboys was born in Birmingham, Warwickshire on 30 March 1921, the son of William and Edith Rose Mortiboys. After leaving school he trained and qualified as a refrigeration engineer, as listed in the 1939 Register, when the Mortiboys family were living at 110, Glastonbury Road in Birmingham.

He joined the Royal Navy as a Direct Entry Acting Engine Room Artificer 4^thClass. A volunteer for ‘Special Service’ he was drafted to HMS VARBEL where he trained as an X-Craft engineer. He was selected for the operational crew of HMS X5.

X5 took part in the attack on the German battleship TIRPITZ in Kaa Fjord, Northern Norway on 22 September 1943. X5, with a passage crew on board, left Loch Cairnbawn on 18 September 1943 and was towed to the operational area by HMS THRASHER (Lieutenant A R Hezlet, RN). The operational crew took over from the passage crew for the approach to the target and the attack. It is known that X5 made its way into the area around the TIRPITZ but was not seen again after being fired at and depth charge attacks.

HMS X5 was lost with its operational crew. Ralph Mortiboys was Mentioned in Despatches (posthumously – see London Gazette of 1 August 1944) “for great daring and enterprise in the attack the German Battleship Tirpitz carried out by Midget Submarines in September 1943“.  He is commemorated on the Portsmouth Naval Memorial on Panel 77, Column 2 and on the 12th Submarine Flotilla memorials at Rothesay on the Isle of Bute and at Kylesku.