History has romanticized Edward VIII as the king of hearts, the man who gave up the throne for the love of an American divorcee, Wallis Simpson. But the truth is far darker, says author Andrew Morton, Princess Diana’s official biographer. In his new book, “17 Carnations: The Royals, the Nazis and the Biggest Cover-Up in History,” Morton unveils how Edward VIII openly sympathized with the Nazis — a fact the British leadership desperately attempted to hide. Here, adapted from his book, Morton reveals the shocking story the royals tried to ban.

In the final days of World War II, US Army Capt. David Silverberg was fighting the stubborn remnants of the Nazi army near the town of Meisdorf in what was to become Communist East Germany.

He spotted an abandoned truck, sprinkled with a confetti of wet and burnt paper. When he examined it more closely, he saw that they were government documents, some signed by Adolf Hitler’s right-hand man, Foreign Minister Joachim von Ribbentrop. Soon he and his men came across fortified buildings stuffed to the rafters with secret Nazi papers.

Days later, a battered metal canister buried on a remote German estate was uncovered. Inside was a microfilm revealing the evil beating heart of the Nazi government machine. The Allied “documents men” realized this find was dynamite and planned to release the damning papers, which revealed in writing the twisted megalomania of Hitler and other top Nazi leaders. They wanted to show the world that the sacrifice had been necessary to overthrow these bloodthirsty tyrants.

Then they came across a file that stopped them in their tracks. It concerned the ex-king of England, now the Duke of Windsor, who had abdicated his throne in 1936 so that he could marry twice-divorced American Wallis Simpson.

That decision rocked the monarchy. Now it was feared that these latest revelations, documents revealing his relationship with Hitler, the secret plot to make him a puppet king after the Nazis had invaded England and his defeatist comments about the necessity for the Germans to bomb Britain into submission, could blow the monarchy sky high.

The 17 carnations

What most people did not realize is that Hitler had spent years courting Edward.

His wooing began soon after he became German chancellor in 1933. He encouraged Princess Friederike, the teenage daughter of German nobility, to romance the bachelor prince. Hitler hoped for a return to the days of Queen Victoria, when English royalty only married German royalty.

Unfortunately for Hitler, Friederike’s aristocratic parents, both ardent Nazis, claimed later that she was too young to marry the future king of England. Instead, Hitler sent a slew of German aristocrats, many blood relatives of the Windsors, to London to collect intelligence on the prince and the rest of the royal family.

They soon discovered that the prince looked west to America when it came to love affairs. Two of his lovers, Thelma Furness and Freda Dudley Ward, had American family connections. They were married, as was his current flame, Wallis Simpson. The German leader sent his trusted emissary von Ribbentrop to court the couple.

He was more successful than Hitler could ever imagined. Within weeks telegrams were flying between Berlin, Washington and London as diplomats gossiped about how Ribbentrop had charmed Mrs. Simpson into bed. He was said to send her 17 carnations, one for every time they had made love, to her apartment of Bryanston Court in central London.

When he heard about the behavior of his right-hand man, even the humorless Herr Hitler joked with him about the saucy stories, according to a Ribbentrop biographer. While Mrs. Simpson always denied the rumors, her great friend Mary Raffray, who ended up becoming Ernest Simpson’s third wife, insisted the torrid tales were true.

Though Ribbentrop courted and charmed Mrs. Simpson, he was focused on seducing the future king and making him a Nazi ally. For a time he was wildly successful. The prince agreed to promote reciprocal visits by German and British war veterans. When he was told off by his father, King George V, for dabbling in politics, he was later seen goose stepping around Mrs. Simpson’s apartment, a storm trooper’s hat on his head.

Like many of his class, Edward was instinctively sympathetic to Hitler’s far-right regime. During the 1920s he had seen the collapse of Weimar Germany, the mass unemployment, crippling inflation and virtual civil war between left and right and believed that a strong leader could restore stability and prosperity.

When (Hitler) occupied the Rhineland in March 1936 — against all international agreements — he relied on the new king to support him.

Moreover the duke loathed Bolshevik Russia and, until his dying day, never forgave or forgot how the Communists ordered the murder of his godfather Tsar Nicholas II and family in 1918. It shaped his political thinking, believing that a strong Germany would act as a bulwark against a resurgent Russia, hoping that one day the two countries would slug it out between themselves while Britain enjoyed the fruits of Empire.

Such was the alarm about Edward’s behavior that Scotland Yard detectives were secretly ordered to follow him and the Simpsons. They discovered that Mrs. Simpson was enjoying another affair with Guy Trundle, a used-car salesman.

At Buckingham Palace and inside Downing Street, the Simpsons were considered blackmailers and Wallis was suspected of spying for the Nazis. The new king was so careless with his red boxes — the state papers that contain top-secret documents about government policy — that some advisors feared that Mrs. Simpson might pass important military secrets to Ribbentrop.

Hitler, though, was delighted with the new king, seeing him as a Nazi ally.

When he occupied the Rhineland in March 1936 — against all international agreements — he relied on the new king to support him. He was not disappointed, Edward Vlll urging the prime minister to take no action against Germany.

‘Operation Cleopatra whim’

Like almost everyone, Hitler was shocked when Edward Vlll gave up his throne in order to marry Mrs. Simpson. He couldn’t understand it. Hitler was a man who wanted to rule the world, Edward had given up an empire for a woman who, by his own admission, he had not even slept with. When they married in a French chateau, only a handful of their friends and none of their family attended, the couple now exiled from England.

The duke and duchess, meanwhile, acted as if World War II was simply a minor inconvenience to their lifestyle.

In 1940, when he and his wife were in Spain and Portugal, Edward had been in secret contact with the Nazis about looking after their luxury villas in Paris and the South of France. The duchess was most concerned that their bed linens be protected from damage. Even the diplomat brother of Spanish dictator Francisco Franco was horrified by the duke’s behavior. “A prince does not ask favours of his country’s enemies. To request the handing over of things he could replace or dispense with is not correct.”

The duchess had other pressing concerns. She had left her favorite Nile green swimsuit behind at their villa in the South of France. It was vital it be returned. To this end she enlisted the American Minister in Lisbon and the American consul in Nice to repatriate the garment. Even though their rented villa was locked and shuttered and that part of the coast occupied by the enemy, the diplomats duly did her bidding.

In the midst of war the swimsuit was found and despatched safely to the grateful duchess. The task was known privately as “Operation Cleopatra Whim.”

Their self-indulgence knew no bounds. With the Nazis poised to invade England in the summer of 1940, Winston Churchill spent precious hours acting as the duke’s travel agent. To keep him out of mischief, Churchill had appointed him governor of the Bahamas. The duke demurred and the prime minister threatened him with court-martial if he did not obey orders.

In the acrimonious back and forth between the two men, the Duke insisted that he could only serve as governor if two serving soldiers were taken out of the army to work as his manservants.

Then the ducal couple wanted to sail to New York on a Madison Avenue shopping trip before he would take up his appointment. By contrast, with a Nazi invasion imminent, the new king and queen were learning how to shoot pistols.

When they sailed for the Bahamas, they left not a moment too soon. For weeks Hitler and Ribbentrop had plotted to kidnap the ex-king and his wife. Hitler had sent his top spymaster, Walter Schellenberg to coordinate a small army of German agents who were poised to snatch the couple from their temporary home in Lisbon. The scheme even had a code name, “Operation Willi.”

The Fuhrer hoped to install Edward back on the throne once the Nazis conquered England.

Hitler had ordered Spanish friends of the duke to try and convince him to stay in Europe, offering him a castle in southern Spain and more than $100 million dollars as sweeteners.

But the duke and duchess were terrified by Nazi-inspired rumors that the British intended to murder them — a reasonable assumption given Churchill’s acrimonious relationship with the ex-king.

Under enormous pressure, the couple to the Bahamas, and Hitler was left empty-handed.

The Windsor file

Though Edward and Wallis were out of sight, the end of the war brought a new headache.

After his abdication, Hitler invited the duke and duchess to visit Germany in October 1937. It was the chance for the duke to show his new wife that though he was no longer king, nothing really had changed. They were met by marching bands and cheering crowds, the duke infamously exchanging Nazi salutes with his hosts. The duke even enjoyed a 50-minute private conversation with Hitler at his mountain retreat.

The potentially incendiary contents of this tête-à-tête remained a mystery even to the “documents men” who pored over top secret Nazi files at the war’s end. King George VI, the duke’s stuttering younger brother who took over when he abdicated, was “deeply agitated” by the existence of the Windsor file.

Even Churchill, who had fallen out with the duke over his wartime behavior, believed the contents of the Windsor dossier should be destroyed lest it damage the standing of the monarchy. They had an ally in Dwight Eisenhower, then Allied supreme commander. He agreed with Churchill and ordered the Windsor file destroyed.

The world would have been no wiser about the antics of the Duke of Windsor but for a couple of American academics. When the order first went out to obliterate the incriminating royal file, Stanford University Prof. David Harris, then working with the State Department, resisted the government Goliath, arguing that it was against the law for government officials to destroy documents. His argument prevailed, causing severe strain to the “special relationship.”

It took the efforts of historian Dr. Paul Sweet to stop the British from delaying publication. In the end the wrangle over the Windsor file lasted longer than World War II itself; it was not until 1957 that the file was published.

The duke escaped largely unscathed, perhaps because he was, by that point, so irrelevant. As for the British monarchy — it still survives in spite of Hitler and his royal allies.

Adapted from “17 Carnations: The Royals, the Nazis and the Biggest Cover Up in History” by Andrew Morton, to be published by Grand Central on March 10.