Betrayal! How the disgraced Duke of Windsor plotted to usurp the young Princess Elizabeth while his brother, the King, lay seriously ill…

The king was sick – very sick. Doctors worried about his future while keeping the severity of his condition a secret from the public.

His immediate family closed ranks to guard his privacy, but in the wider royal circle they were already planning. A plan to abandon the age-old succession order and put a usurper on the throne.

The king in question was not Charles, but his grandfather, King George VI.

In the few weeks that the king disappeared from public view in the spring of 1949, the course of history could well have changed – and not for the better.

The plot began when the king, known as Bertie, was admitted to hospital for an operation to sever a nerve at the base of his spine.

The risky procedure was intended to counteract the artereosclerosis he suffered from too much stress and too many cigarettes.

Bertie was a man struggling with ill health and although he would eventually recover and live on, this was a serious operation. He was in danger of losing his life.

What would happen if he suddenly left – or worse, stuck around?

At Buckingham Palace, the courtiers were in a downward spiral.

It’s hard to imagine now, but they were terrified of the influence Prince Philip had over Princess Elizabeth, his wife, over the past two years.

Not only did the palace’s old guard deeply dislike Philip, but their suspicion and distrust also extended to his uncle, Lord Mountbatten.

Mountbatten, a cunning old schemer, was loathed for planting his pushy nephew in the princess’s way – for none of the dour brigade could bring themselves to believe that she could actually have fallen in love with the handsome sailor.

They feared that Elizabeth would become Lord Mountbatten’s poodle.

At 23, she was far too young and impressionable to take up the challenge of head of state.

Mountbatten must be kept away from the instruments of power.

And so – quickly – talk grew of putting a regent on the throne if King George VI were to remain in office but were no longer able to fulfill his constitutional role.

Enter the Machiavellian figure of Kenneth de Courcy, a petty aristocrat with a penchant for intrigue, interference and deceit.

Born in Ireland, De Courcy had made his money by creating conspiracy theories and then selling them through a number of publications he owned.

He had become a close friend and advisor to a man who had many connections but was never known as a good judge of character: the Duke of Windsor.

What happened between the two over the next few weeks amounted to nothing less than betrayal.

Since the declaration of peace in 1945, De Courcy had whispered in the duke’s ear that – at home – the royal front line was weak.

The Duke and Duchess of Windsor, now based in France, relied on De Courcy and his high-level social contacts to gather all the palace gossip in London.

So they listened intently as the Irishman explained his plan.

If a regent was suddenly needed, he argued, who would they call? Old Queen Mary, widow of King George V and mother of the ailing king, was in her 80s. She looked like a remote and anachronistic figure.

There was the Duke of Gloucester, another brother of George VI and the Duke, but he was regarded as a joke by courtiers and politicians and by the royal family itself. (His name was Harry!).

There were no other close claimants to the throne.

All the Duke of Windsor had to do was play his cards right, De Courcy whispered, and the throne could be his – at least until young Elizabeth came of age.

“The King is seriously ill and out of circulation,” he wrote to the Windsors, “and will be out of circulation – facing the terrible tragedy of losing first one leg and then the other. He is suffering from a serious illness that is incurable and has spread throughout his body.’

These were lies, but they played a role in his story.

“I must tell you in confidence that there has been talk of a regency,” he continued, “and it seems likely that one will be appointed.”

So now he outlined to the Duke the details of his plot.

‘I should like to see you buy some farmland near London, and devote a large part of your time to experimental farming on the most advanced modern lines. This would be a great attraction for the country.’

Be there, standing in the wings, was his message. People are very suspicious of Mountbatten’s influence and remember your glory days as Prince of Wales. Elizabeth is too young – you have the track record.

He made no mention of the abdication.

Windsor took the bait. “We discussed that subject in Paris,” he replied to De Courcy.

‘It is certainly a matter of great delicacy, but at the same time an issue where it seems as if I have 50 percent of the negotiating power. I’d rather not say anything more about it in this letter, but I look forward to a future conversation with you.’

Wallis, his duchess, was involved in the plot.

“We’re always turning things around in our heads,” she wrote back.

‘There’s no doubt that something can be done – and perhaps a good thunderstorm would clear the sky. Anyway, I can’t sit around and watch the Duke get lost.’

Undoubtedly there existed in de Courcy’s mind a divide-and-conquer strategy worthy of the Tudor court.

If the duke were to succeed in gaining the regency, he would be in a position to expel the courtiers who disliked and distrusted him and appoint his own deputies.

Thus fortified, he could take on the politicians – and either win them over or deny them access to the palace, with all the privileges that traditionally come with close contact with the royal family. Politicians love those palace invitations!

It was treacherous to try to deny young Elizabeth her birthright, the throne. But with a fair wind it might be doable – if King George VI were to stick around for a while.

But it never happened.

Why not? Nobody really knows. Windsor certainly had the discussions, the thought of usurping his niece – even for a short period of time – was on his mind. We know this much from his secret correspondence.

Perhaps the man who thought he could make Wallis Simpson his queen and weather the abdication storm suddenly remembered that the British establishment can, if it wants to, fend off a king.

He didn’t have the courage for that fight.