The glamorous Monégasque royals' position atop their throne hasn’t always been guaranteed.

In the new Curiosity Stream documentaryRoyals: Keeping the Crown,Prince Rainier of Monacohits a crisis point in his reign that almost gave the world Princess Marilyn instead of Princess Grace.

Shortly after World War II, Monaco — like so many other European countries — was financially and culturally ravaged, and a longstanding agreement with France meant the prince’s crown was in danger of being lost if Rainier couldn’t revive his country’s primary industry of tourism. Add to that, Rainier was also an unmarried man who had yet to produce a son to inherit his seat on the famous gambling destination’s throne.

According to University of St. Andrews historian Dr. Chandrika Kaul, “Prince Rainier is now 32, and the idea that he might lose his principality if he doesn’t marry well and produce a male heir is uppermost in his mind.”

Adds Royal historian Kate Williams, “The stakes couldn’t be higher — Monaco is under threat. It could collapse, and Rainier has to save it.”

“Prince Rainier was advised that he would do well to marry a Hollywood ‘princess,’ and [capitalize on] all the celebrity and fame that went with that marriage,” says Dr. Kaul. “What Monaco needed was to revive its tourism trade. It made perfect economic sense.”

EnterMarilyn Monroe— almost…

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Prince Rainier, mailyn monroe

According to theKeeping the Crown, Monroe was the first suggestion on the prince’s list — but theSome Like It Hotstar had an overly sensual image, which struck her from the list.

“The executive atParis Matchthink that this will be a really dramatic, sensational meeting between the Queen of Hollywood and their own Prince, who is an eligible, young, handsome bachelor — who also just happens, rumor has it, to be looking for a wife,” says Dr. Kaul.

Grace Kelly and Prince Rainier in 1956.Keystone/Getty

Prince Rainier

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Royal watchers know how this story played out, with the prince sweeping the starlet off her feet and the couplemarryingless than a year later on April 18, 1956.

Prince Rainier and the newly minted Princess Grace went on to have three children:Princess Caroline,Prince AlbertandPrincess Stephanie.

“It was such an incredible affair, and it’s left such a mark on people,” Alberttold PEOPLEin 2017 of his parents' wedding. “What it has meant for people has been incredible. For us, it was …our parents getting married. But what it’s meant for Monaco, for people around the world, and, how their story continues to fascinate people, that’s something unimaginable.”

All six episodes ofRoyals: Keeping the Crowndebut onCuriosity StreamThursday at 9 a.m. ET.

source: people.com