Often dismissed by history as a frivolous playboy with an unhealthy penchant for martinis and morphine, the late Queen’s uncle, the Duke of Kent, had a surprising depth to him.

The Daily Mail can reveal today the cloak-and-dagger part the duke played as a rogue secret agent in the run-up to the Second World War.

Unlike his eldest brother, the Duke of Windsor, who is often remembered for his association with Adolf Hitler, Georgie, as he was called, held contrary views. Viewing the Nazis as a menace to freedom, he attempted to prevent war as early as 1938.

In defiance of the then Prime Minister Neville Chamberlain’s directives, the duke entered into clandestine discussions with Prince Philipp of Hesse, a prominent Nazi.

The relationship was facilitated by the fact that Philipp was the duke’s cousin through marriage. Despite his alignment with the Nazi regime, Philipp was concerned by the extreme policies of Joachim von Ribbentrop, Hitler’s associate. Like Georgie, he also yearned for peace before global conflict ensued.

Georgie Kent was deeply driven in his role as an covert operative. He had the backing of his brother, King George VI, who urged him to collaborate with Philipp under the notion that if politicians failed to broker peace, then perhaps their royal peers could show them how it’s done.

Historian Tom MacDonnell concurs: ‘King George VI was shadowed by the memories of World War I. He consistently offered to personally appeal to Hitler, believing in the lingering power of kings and princes in diplomacy, as if the geopolitical changes since 1914, when Europe was a playground of royal cousins, hadn’t occurred.’

The Duke of Kent was a patriot who believed in his country. But – possibly even more important than his point of view – it was the fate of his wife Princess Marina’s Europe-based family, likely to bear the brunt of an armed Nazi assault much earlier in the war, which drove him.

Coolly elegant Marina – more royal than the British royals through her line of descent from the tsars of Russia and the kings of Greece – was also closely connected to other countries and their ruling houses.

Her sister Olga was married to the prince regent (de facto king) of Yugoslavia, while her other sister Elizabeth was married to a German aristocrat Count Toerring-Jettenbach. She was related to the queen of the Belgians, and was a first cousin of Prince Philip, future husband of Queen Elizabeth II.

So, increasingly alarmed at the speed with which Europe was crumbling, Georgie was introduced to Baron William de Ropp, a shady figure and possible double agent whose German contact was Nazi leader Alfred Rosenberg, later hanged for his part in wartime atrocities.

Ropp and Georgie’s meetings were important, frequent, and very hush-hush. Professor Jonathan Petropoulos, an expert on German royals and the Nazi regime, observes: ‘The Duke of Kent obviously had a very real influence on political events. He was uniquely placed to act as an intermediary between high-ranking Nazis and the movers and shakers of British society. It was an opportunity he seemed to relish.’

The upshot was two crucial meetings. In July 1938 Georgie and Philipp had a private conversation in Rome. Ostensibly there for the funeral of Queen Marie of Romania, they were closeted away in lengthy private discussions. Then the two royals met again in Florence a year later – against prime minister Chamberlain’s wishes.

‘Chamberlain wanted to constrain the royals, because the situation in Europe was too complicated and unsettled to entrust negotiations to amateurs such as the duke and the prince, and dismissed a suggestion by King George VI that they use Prince Philipp,” wrote Petropoulos.

But Georgie went ahead anyway and, with the war now just weeks away, met Philipp in Florence in July 1939. ‘It directly contravened the instructions of the prime minister,’ observed Petropoulos. Georgie made it clear to his cousin that Britain would declare war if the Nazis entered Poland, and Philipp took this information back to a meeting with Hitler, at which Ribbentrop was also present.

The difficulty for British politicians with all this clandestine activity was, what was a legitimate path to peace, and what was appeasement?

There are no official records of what was said between the cousins during their confidential meetings. Spymaster Frederick Winterbotham, who had spent the pre-war years recruiting spies across Europe, was the shady Baron de Ropp’s ‘control’ during this period. In 1969 he published a book, Secret And Personal, which devoted a chapter to the Ropp-George meetings.

But by the time a second edition was published the chapter had been dropped, apparently at the request of Buckingham Palace. Even 15 years after the war’s end – and 17 years since George’s tragic death in an aeroplane crash – the contents were deemed inappropriate.

For a royal to disobey their prime minister was one thing. For the royal to do so as war approached was far worse. That George may, in the course of his discussions, have passed on highly classified secrets – either inadvertently or knowingly – to a man who soon would fly to Hitler’s side was unthinkable.

Which is why the world has never learned about the Duke of Kent, Secret Agent. The records are either locked up or destroyed, and we will never know whether he did a good thing, or a bad thing, in his personal efforts to secure peace.

And so all that remains of poor Georgie is the memory of a playboy without a purpose.