Son of Italy's last king causes storm with Juan Carlos comments.

A new Netflix series on the last heir to Italy's defunct throne includes an explosive claim by the 86-year-old prince about Spain's former king Juan Carlos.

Titled The King Who Never Was, the three-part docuseries traces the story of Prince Vittorio Emanuele di Savoia who left Italy in exile at the age of nine after Italians voted to abolish the monarchy in 1946.

The prince is the son of King Umberto II who ruled for only 34 days after his father, King Vittorio Emmanuele III, abdicated due to being discredited by his support for Mussolini during world war two.

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The Netflix series is centred on the tragic events that occurred on the night of 18 August 1978 at Cavallo, a small French island off Corsica, where the prince had been holidaying at the time.

After a group of young friends took a dinghy attached to his boat, he reacted by confronting them angrily with a rifle, which he fired, resulting in a 19-year-old German man being shot accidentally.

Dirk Hamer, who was hit by a bullet while he lay sleeping in a nearby boat, died of his injuries on 7 December 1978 and the crown prince was subsequently arrested.

The Netflix series charts the scandal surrounding the ensuing court case amid accusations of disappearing evidence, vanishing documents, incomplete investigations and allegations of witness intimidation.

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However the new series is making headlines in Italy for a different gun death, involving a member of the Spanish royal family, that occurred in 1956.

At the end of the series, the aging Vittorio Emanuele makes unexpected off-air comments involving Spain's former king Juan Carlos and his younger brother Alfonso of Bourbon, who died of an accidental gun shot wound aged 14.

Speaking of the royal teen's death, Vittorio Emanuele said: "It was Juan Carlos who killed him, I was there".

In an interview with Italian newspaper Corriere della Sera on Thursday, the director of The King Who Never Was, journalist Beatrice Borromeo, said of the Cavallo incident: "We are talking about a matter that many thought they knew, but which was shrouded in confusion. For the first time in over 40 years we have managed to get all the protagonists and eyewitnesses of that night to speak."

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Describing Vittorio Emanuele's comments regarding Juan Carlos as "a scoop", Borromeo said: "I was amazed that in the first days after the launch no one spoke of that recording, which is essential for truly understanding the story of Vittorio Emanuele."

She claims that although it may seem "disconnected" from the rest of the documentary to the casual observer, "the fact that Savoia, during his adolescence, in the years in which he learns everything about the world, witnessed an incident similar to his, which caused a death immediately covered up, is the missing piece to really understand the events of Cavallo."

Borromeo told the Corriere that Vittorio Emanuele "repeated the story of Juan Carlos several times following his interview, with me and then with other members of the crew. It was he himself, spontaneously, who linked the two events. I think he did so because of the profound similarity between them, both for the dynamics of the incidents and for how they were handled afterwards."

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Acknowledging that it was "delicate material", she stressed that Vittorio Emanuele "wanted to share" the story with us, adding: "It was right to share it with the public."

The prince's son, Emanuele Filiberto, disagrees however, describing his "bitterness" over Borromeo's decision to include the comments.

"Let's say I thought it would be about my father's life and I later discovered that it was almost exclusively about the story of Cavallo", Emanuele Filiberto told the Corriere.

"King Juan Carlos involved in the incident that claimed his brother's life when they were kids? It's not a new story and also I wasn't there when the off-air remarks were made", he stressed, concluding: "My father and I regret very much that these comments have come out, they have no reason to be in the documentary that deals with something else", he concluded.

Cover photo Netflix - The King Who Never Was