The P311 left Malta in December of 1942 with a crew of 71 submariners to participate in an Allied attack on Italian warships off Sardinia, but vanished in January 1943, most likely after hitting a mine.

HMS P311 was the only boat of her class never to be given a name. She was to have recieved the name HMS Tutankhamen but was lost before this was formally done.

Mr Bondone, known as the "wreck hunter", told local media:

"Immediately I thought of the destiny of the men who met their deaths down there.

"It was a fate shared by so many men, submariners in particular, on both sides of the conflict."

Local fisherman at the time reported hearing a loud rumble at night, according to La Nuova Sardegna.

Paola Pegoraro of the L’Orso diving club, which provided logistics for Mr Bondone's shipwreck search operation, told The Telegraph that Mr Bondone was able to positively identify the submarine as the P311 by the two Chariot-style “human torpedoes” that are affixed to the outside of the vessel.