SITTING on a throne in Notre Dame cathedral, Napoleon Bonaparte held a golden laurel wreath crown like Caesar’s aloft as he declared himself Emperor of France.

But as new blockbuster film Napoleon from Gladiator director Sir Ridley Scott will show, this “lover, tyrant, legend” who inspired a swathe of remarkable victories across Europe was ultimately defeated when it came to the woman he loved.

The power-mad dictator’s first wife Josephine de Beauharnais cheated on him within weeks of their wedding, yet Napoleon refused to give her up.

Even while he was leading his men into battle, his lust for the society beauty barely waned, and he wrote her a stream of “dirty letters”, at one point urging her not to wash for three days until he returned from one campaign.

He talked about Josephine’s talent for an undefined sex act called zig-zags, and had a pet name for her private parts, which he dubbed the Baron de Kepen.

Vanessa Kirby, 35, plays Josephine in the risque epic and says she was the power behind the throne and an “incredible force of nature”.

The couple “were deeply attached to each other”, she explains.

Vanessa, who also portrayed Princess Margaret in The Crown, found “compassion” for Josephine “because it was a brutal time and he was brutal to be with”.

The film does not shy away from depicting the tumultuous, sex-fuelled love affair, with some scenes already courting controversy.

Lead actor Joaquin Phoenix, 49, came under fire after it emerged he spontaneously slapped Vanessa during a fight scene because he wanted to “surprise her”.

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She insists she felt “safe” and the passion between Napoleon and his wife meant the actors went to “dark places together”.

Napoleon was certainly not born to be a leader of France.

He came from Italian nobility and French was his third language — after Italian and Corsican. At 5ft 6in he was also bullied at school.

But his dislike for the monarchy put him on the right side of history when there was a revolution against the king at the end of the 18th century.

Napoleon distinguished himself against royalist forces at the Siege of Toulon in 1793 and, two years later, on the streets of Paris.

Seeing off the king’s supporters earned him fame and the attention of Josephine, six years his senior and previously married.

Mission: Impossible actress Vanessa says: “She was not a person anyone wanted to marry.

“She was a widow with two children and six years older than he was.

“But she captivated him. There was something they had in common. They understand each other as outliers.”

While the often jealous, insecure Napoleon had more than 20 affairs during his marriage, his early sexual experiences were as humiliating as his final defeat at the Battle of Waterloo in 1815.

He lost his virginity in a Paris brothel, which historian Andrew Roberts, who presented a BBC series on Napoleon, called “a particularly mucky experience”.

The military hardman failed to have sex with three prostitutes before finally succeeding with the fourth.

When they married in 1796, he was less sexually experienced than Josephine, whose first husband Alexandre de Beauharnais had been guillotined by French revolutionaries before she became a favourite mistress of new leader Paul Barras.

But two days after their wedding Napoleon was sent to Italy to command the French army and, within a couple of weeks, his bride had found a replacement lover.

Professor Michael Broers, a University of Oxford academic who has written a biography of Napoleon, tells The Sun: “In the early years she treated him like dirt. She was having affairs under his nose.

“When he returns from the Egyptian campaign she’s having a liaison with another man.

“He has to go down to the cafe down the road to get the spare key to get into their home.”

Contrary to his famous phrase supposedly spurning his wife’s overtures, “Not tonight, Josephine”, Napoleon remained infatuated by her.

Despite affairs on both sides, he wrote passionate letters to Josephine, some of which were X-rated.

One, apparently written on November 21, 1796, while he was away on the first Italian campaign, made reference to his famously generous style of love making.

It read: “How happy I would be if I could assist you at your undressing, the little firm white breast, the adorable face, the hair tied up in a scarf a la creole.

“I will never forget the little visits, you know, the little black forest?.?.?.?I kiss it a thousand times and wait impatiently for the moment I will be in it. To live within Josephine is to live in the Elysian fields.”

Ridley Scott says: “His letters to her are comically rude and juvenile, overly romantic and even quite dirty.”

But the director thinks Josephine was not impressed by Napoleon’s romantic scribblings, saying: “She never even read them.”

Prof Broers, a historical adviser on the film, thinks some of the “really dirty” letters were forgeries.

What is in no doubt, though, is how conflicted Napoleon was by his love for Josephine.

Crowning himself Emperor of France in 1804, he was desperate to have an heir who could carry on his dynasty.

The problem was that his wife was unable to bear his child.

He avoided ending the marriage until he dodged death during his defeat of Austrian forces in 1809.

That made Napoleon determined to find a new wife who could give him a son before he passed away, and the pregnancy of a mistress, Countess Walewska, convinced him the fertility problem did not lie at his door.

Prof Broers says: “In Austria, he’s really ill and someone tries to assassinate him.

“He survives and that’s when he decides he needs to do it.”

Napoleon asked others to break the bad news to Josephine, but they refused.

The professor explains: “He can lead men in battle, he gets wounded, someone tries to kill him, but telling his wife he wants a divorce? He doesn’t want to do it.”

When Josephine was finally told, in December 1809, her screams could be heard all over the Tuileries palace.

She collapsed on the floor and Napoleon and another man had to carry her to her apartments.

Even during the divorce proceedings in January 1810, he almost changed his mind.

But Napoleon did not waste any time finding a new bride, marrying Mary Louise, the 18-year-old daughter of the Emperor of Austria, three months later.

By the following year they had a son, Napoleon II.

All hopes of his heir taking over power were undone by Napoleon’s unbridled ambition.

In 1812 he decided to invade Russia, a campaign which was to end with him losing most of his 400,000 troops.

In 1813 Britain, Russia, Prussia, Austria, Sweden, Spain and Portugal joined forces to take on France.

By the end of March 1814, those allied forces marched into Paris and — by the next week — Napoleon was forced to abdicate.

Yet even being sent to exile on the island of Elba could not end the terrible bloodshed.

Napoleon managed to escape, retake control of the French army and march on British forces commanded by the Duke of Wellington in June 1815.

Prof Broers says: “He was always convinced that Wellington wasn’t a great general.”

Wellington’s men, supported late on by Prussian forces, proved him wrong by emerging victorious at Waterloo.

This time the British made sure Napoleon could not escape, by sending him to the island of St Helena thousands of miles away in the Atlantic Ocean.

Napoleon died on the windswept rock at the age of 51 in May 1821.

It is estimated that between five million and seven million people died during the Napoleonic Wars.

Such suffering has led some historians and Sir Ridley to compare Napoleon to the most murderous despots in Europe’s history — Germany’s Adolf Hitler and Russia’s Joseph Stalin.

But Prof Broers does not place the French dictator in such reviled company.

He says: “He was a soldier, he didn’t worry about casualties, he could be ruthless, but he wasn’t a sadist.”

Napoleon II died aged 21 in 1832 from tuberculosis and had no heirs.

So his father’s decision to end his marriage to Josephine had been futile.

In an odd footnote to history, Napoleon’s penis was allegedly amputated during an autopsy and has passed through several owners.

It now resides in New Jersey with Evan Lattimer, whose father John, a renowned urologist, bought it at a Paris auction for $3,000 in 1977.

“It’s very small, but it’s famous for being small. It’s perfect structurally,” Evan has said.

Josephine, meanwhile, was given a generous settlement and lived at Malmaison, outside Paris, until her death there aged 50 in 1814.

Sir Ridley said: “Napoleon has always fascinated me. He came out of nowhere to rule everything, but in the meantime he was waging a romantic war with his adulterous wife.

“He conquered the world to try to win her love, and when he couldn’t, he conquered it to destroy her. And he destroyed himself in the process.”

When Napoleon was told Josephine had died of a broken heart, he was pleased and said: “She really loved me, didn’t she?” On St Helena, he told others what she meant to him.

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Prof Broers adds: “He said he really liked his second wife Mary Louise, saying, ‘She’s brave, she’s intelligent, loyal, she would make a good ruler — but I loved Josephine’.”

  • Napoleon will be in cinemas from November 22.