Of the dozens of books written about Wallis Simpson, the Duchess of Windsor, the latest is surely the strangest. Michael Bloch, its author, says she was born a man. Fellow biographer Hugo Vickers takes him to task
The Duke of Windsor has been the subject of a great number of biographies, beginning with those published in his early years and accounts of his extensive travels, and ending, or so we hoped, with Philip Ziegler's authorised life, Edward VIII, in 1990. Both the Duke and the Duchess wrote their memoirs (with the help of ghosts) in the 1950s. There have been documentaries, including a rather disreputable one last year called The Traitor King and Prince Edward's more balanced approach, Edward on Edward, which corrected some of the untruths and appears to have launched the Duke's great-nephew on a career as an assured television presenter.

I am sometimes described as a Duke of Windsor expert myself, though I have only contributed a text to the handsome book of photographs, found in the Duke's bath, The Private World of the Duke and Duchess of Windsor. Nevertheless my interest goes back to the 1960s. I was fortunate to go to the Duke's house in 1972 and again several times after his death, during which time I got to know his private secretary, John Utter. I therefore witnessed the decline and the exchange of power, first from the private secretary to the personal secretary and then to the Duchess of Windsor's lawyer, Maitre Suzanne Blum.

It was chilling to hear what was happening. In the early days Blum was spoken of as a very good lawyer, zealous in her handling of the Windsors' affairs. When the Duchess had a problem, Blum would be summoned, just as any of us might summon a lawyer for protection. But then suddenly in 1978 she took control.

Thereafter writers and publishers who dared to write about the Duke and Duchess of Windsor could expect a torrent of abuse and threats of legal action to wing their way from Paris. These threats came from Blum, who had assumed the position of "defender of the moral rights and interests of the Duchess of Windsor" (to use her own words). Blum was in more or less sole charge of the Duchess of Windsor's affairs until the Duchess died in 1986.

Then on to the scene came Michael Bloch, a young English lawyer who went to work as her pupil. Sometimes the warnings were drafted by Bloch, in whom Blum had considerable confidence. "Michael sait tout!" the Maitre once told me, presumably in a spirit of reassurance.

Blum authorised Bloch to publish a number of books about the Windsors, giving what he likes to call "their point of view". At the time we were led to believe that the Duchess of Windsor was authorising these publications but no one believes that any more. The true motive for Blum's rage against independent writers became clearer when the poor Duchess eventually died. Hardly was her body cold than the letters and notes written between Duke and Duchess began to appear in the press and a few days later a book, edited by Bloch, appeared, the preface of which was dated, with consummate lack of taste, on the very day of the Duchess's demise.

Bloch produced one or two more volumes on the Windsors, but then it seemed at last that he had milked that story dry and he proceeded to write a life of Ribbentrop. He is said to be working on a life of Jeremy Thorpe. Since he is no mean researcher and no fool, I am sure he has coped well with these assignments. It is when he writes of the Windsors that he loses his perspective.

In returning to his Windsor yoke, he makes, I believe, mistakes. He may have been spurred to this new publication after his treatment by the late Lady Caroline Blackwood in her book, The Last of the Duchess, which caused him to moan: "Now I am famous..." He would have been yet more famous had cautious lawyers not removed a devastating description of him in Lady Caroline's original manuscript concerning his tongue.

Bloch's latest suggestion is that the Duchess of Windsor was a man. That was the shock headline served up this week in extracts from his biography published in the Daily Mail. To be fair to him, what Bloch actually suggests is that the Duke of Windsor "never in fact enjoyed full marital relations with her and she was probably incapable of them". He suggests that she was a victim of AIS which, Bloch explains, means that the child is born with the male XY chromosome but develops externally as a female, though with no internal reproductive organs. Bloch, once a lawyer, advances this theory because in 1980 a "delightful" doctor told him in the Savile Club: "There's no doubt of it, for I've heard the details from a colleague who examined her. She's a man". Bloch asked no more and the delightful doctor died in 1982. Nevertheless this is the introduction to his new thesis.

How low can he stoop to gain serialisation for his book? A man who says he is a serious historian cannot make such claims and expect to be taken seriously. Trained as a lawyer, he should have delved a little deeper and had his story categorically denied. Why did he not consult Dr Jean Thin, who contributed to his book The Secret File of the Duke of Windsor? Thin had the Duchess at his mercy for many years while she was a patient locked from the world in her house in the Bois de Boulogne. He must have examined his comatose patient. He could have clinched the matter at once.

We live in an age of sensation and wherever there is a celebrated story, there is an opening for ludicrous exaggeration. Bloch must know that his suggestion is rubbish but he cannot resist the tabloid shilling. For these days, alas, many readers care little whether what they read is true or false so long as it is sufficiently diverting.

The abdication is one of those stories that will be discussed long after all the protagonists are dead. The role of Mrs Simpson is intriguing. She has always been surrounded by weird myths. The traditional line was that she captivated the Duke of Windsor having acquired "special ways" in China. While the girls in the bars stooped down to pick up pennies, employing what the French called the "Cleopatra clip", Mrs Simpson was able to pick up a Sovereign, ho, ho.

Then there were those old jokes about the Duke of Windsor. "He started off as Admiral of the Fleet and ended up as third mate on an old tramp."

Having studied the Windsor story for many years, I agree with some of Bloch's saner theories, among them that the King wanted to go. He had always been attracted by the newness of America and I cannot help feeling that he found the court and formality of court life stuffy beyond imagination. I am sure that Mrs Simpson liked being the King's "friend" but was perhaps less happy to be the wife of the exiled Duke of Windsor. The position of King's friend meant that the great men of the day took her seriously and played up to her to be in the King's favour. She was horrified at the thought of abdication.

The Duke suffered because he felt he had failed his wife on two counts. He was unable to get her the title of Royal Highness and he was unable to get her received by his family.

I also agree with Bloch that the reason the Duke went to Germany was on a peace mission, inspired by a letter from an American called Selbert and with his own memories of the carnage of the First World War in the forefront of his mind. So I agree with much, but Bloch ruins his credibility with his other nonsense.

What more can be said about the whole of the Windsors, the love story of the King who gave up his Empire for the woman he loved? Very little, I suspect. What is needed now is not another rehash of the abdication, wrapped up in bizarre theories impossible to substantiate, but a clinical analysis of exactly what did happen in the last days of the Duchess when Maitre Blum held sway. It will not make pleasant reading.