1941 1942 1943 1944 1945 The auxiliary ship Olterra was a 5,000 ton Italian tanker scuttled by her own crew at Algeciras in the Bay of Gibraltar on 10 June 1940, after the entry of Italy in World War II.

She was recovered in 1942 by a special unit of the Decima Flottiglia MAS to be used as an undercover base for manned torpedoes in order to attack Allied shipping at Gibraltar.

After the attacks carried out by Scirè, the commander of the Decima MAS realised that, given the limitations of using a submarine as a mother ship for human torpedoes in Gibraltar, it would be more feasible to mount a secret base in neutral Spain.

A first step in that direction was taken when a member of the Decima, Antonio Ramognino, rented a bungalow along the coast road near Algeciras, right in front of a bay used by Allied convoys to drop anchors.

[14] At the same time, another officer of the Italian special unit, Lieutenant Licio Visintini, himself a veteran of previous submarine incursions against the "Rock", learned about Olterra and conceived the idea of a secret mother ship for the maiali.

Under the pretext of raising the ship to sell it to a Spanish owner, a team of members of the Decima, disguised as Italian civilian workers, took control of the tanker.

They had remained on board the half sunken oiler along with a Spanish guard for more than two years, in order to protect the rights of the Italian company which owned Olterra.

[16] Once at docks, some of Olterra's cargo holds and a boiler room were modified by Visintini men into a workshop for the assembling and maintenance of human torpedoes.

A scene of civilian sailors working to overhaul the ship was meanwhile set up for the outsiders, in order to deceive both British and Spanish authorities.

The motor launches and sentries inside the British base were quietly active and alert, conscious of the danger of a potential attack on the fleet at anchor.

One of the security measures taken by the Royal Navy after the summer incursions of combat swimmers was the deployment at Gibraltar of an underwater bomb disposal unit, under the command of Lieutenant Lionel Crabb.

After a long chase by anti-submarine boats, the Italian crew decided to scuttle their craft and took shelter on board an American freighter.

The last manned torpedo was caught in the middle of the general alarm across the stronghold, but managed to slip beneath the waters and fool the submarine chasers.

The copilot, Leone, became missing during the pursuit and was never found; Cella, meanwhile, abandoned the craft elsewhere, thinking that he was still near Gibraltar or, in the best case, stranded close to the Spanish coast.

With the idea of becoming a prisoner of war or being arrested and interned by Spanish authorities in mind, Cella surfaced, only to find that he was just a few meters away from Olterra.

[25] The end of the war in North Africa and the subsequent Allied landings on Sicily also made the attacks on logistic ships a priority.

In order to divert any British suspicion from Olterra, the selected targets were merchant ships at anchor in the farthest point from Algeciras.

The gale that was raging at the time hampered the mission, because the current forced them to dive around the targets before they could attach the limpet mines to the hulls.

To mislead the British into thinking of combat swimmers instead of manned torpedoes, members of the Italian secret service scattered diving equipment along the shore.

In Leon Goldsworthy's words:The Spanish authorities tried to hide the evidence, but when Crabb’s diving team boarded Olterra after the Italian armistice, they found spare parts from three different torpedoes.