A MYSTERIOUS relic of Empire that lay hidden in a North-East library for decades has led history detectives to the final resting place of a long-lost Second World War submarine.

The Italian vessel Macalle sank after hitting a coral reef off the coast of Sudan, east Africa, in June 1940 while hunting for British warships.

Despite suffering methyl chloride poisoning while still on board and having to survive ten days in crippling 60 degree heat on the tiny island of Barra Musa Kebir waiting to be rescued, all but one of the Macalle’s 45-strong crew survived the ordeal.

But the submarine’s precise location was lost to history – until Argentine-Italian filmmaker Ricardo Preve traced the diary of crewmember Adriano Tovo to Durham University’s Palace Green Library, which had been gifted the journal by the widow of Port Sudan’s last British harbourmaster.

The discovery prompted an expedition to the Red Sea, where divers found an antenna mast 55m below sea level, pieces of bent and twisted metal and a large break in the coral reef consistent with a submarine crashing through it – leading the team to declare they now know where the Macalle rests.

Diver Ivan Markovic said: “We were all absolutely thrilled to find the antenna and the disturbed coral, knowing that the Macalle was hundreds of metres below us. Its whereabouts has eluded many dive teams over the decades and it was an incredible experience to be part of the team that has finally solved this mystery from World War Two.”

Plans are now afoot for a return mission with the support of the Italian Navy and equipment capable of reaching the Macalle at 400m deep.

The Durham diary also led Mr Preve to the long-lost grave of the one Macalle crewmember to die, Carlo Acefalo, who was buried in the sand of Barra Musa Kebir.

The filmmaker visited the site to place to pay his respects and place an Italian naval flag.

“Finding what could be the grave of this young Italian sailor was a very emotional moment for us,” Mr Preve said.

"To think that someone had been left behind for 75 years and was only now beginning a journey home to Italy was very moving. It all matched: the different structure of the grave than others found on the island, the metal cylinder. We noticed that the grave was placed facing Italy."

The Italian and Sudanese governments are now discussing testing the bones to confirm the body is that of Acefalo.

Durham University is home to the Sudan Archive, which was founded in 1957, the year of Sudanese independence, to preserve documents from the period of Anglo-Egyptian rule of 1899-1956.