WCXX

Yet inevitably it is their sex life that has filled tomes, because in sex, we believe, a person's deepest essence is revealed. Rumours of homosexuality had dogged Hitler since the early Twenties, repeated in Munich newspapers and bolstered by his close relationship with Ernst Röhm, the homosexual head of the Sturmabteilung, the Nazi Party militia.

There is good reason to believe that he did have repressed homosexual tendencies, yet the dictator's interest in women is also well-attested. He would invite actresses back to his apartment for "private performances". One actress, Renata Müller, spread rumours about Hitler's alleged proclivity for self-abasement, with suggestions that he knelt at her feet and asked her to kick him. When she fell to her death from a window in 1937, many questioned the verdict of suicide.

Even more eye-catching was the secret 1943 report from America's Office of Strategic Services (forerunner of the CIA) which labelled Hitler an "impotent coprophile". Based on claims from Otto Strasser, one of Hitler's opponents in the Party, it alleged that the dictator forced his niece Geli to urinate and defecate on him. While it is hard to separate reality from politically inspired propaganda, Hitler's obsession with the unfortunate Geli was probably the deepest of his life, and her suicide in his apartment brought him close to breakdown. Geli, like Eva, did not threaten him intellectually. "There is surely nothing finer than to educate a young thing for oneself," he opined. "A lass of 18 or 20 years old is as pliable as wax."

It is impossible to peer behind the bedroom door, but Amis's speculation that Hitler was "sexually a void", because of his obsession with hygiene, is contradicted by observers at the time, who suggest that Hitler and Eva did share a bed as a couple. They had interconnecting bedrooms at the Berghof and Hitler's valet, Heinz Linge, attests that they would go to bed together.

^{Evidence suggests that Adolf Hitler and Eva Braun did share a bed as a couple}

While Hitler's maid, Pauline Kohler, wrote that "Hitler is not strongly sexed", Eva Braun's correspondence reveals nothing unusual – certainly not along the lines of fully clothed sex – except that once war had broken out, Hitler was unable to get interested. She used to show her friends a 1938 photograph of Neville Chamberlain on a sofa in Hitler's Munich flat, saying: "If only he knew what goings-on that sofa has seen!"

It would be surprising, as Amis says, that such a warped psychology as Hitler's could ever be "a considerate and energetic lover". Yet, once I began to write about the Nazi wives, I realised that the ability of mass murderers to compartmentalise their lives is one of their most disturbing aspects.

A new documentary about Himmler's home life, called The Decent One, by the acclaimed filmmaker Vanessa Lapa, focuses on the tender personal letters between Himmler and his wife Marga, largely about their daughter Puppi, even as he perpetrated daily atrocities. It raises the same questions as Thomas Harding's book Hanns and Rudolf, about the private life of Rudolf Höss, the Auschwitz commandant, whose children played just yards away from the camp, oblivious of the horrors occurring there.

Looking at the women who loved the Nazis is not prurient. It matters because viewing the Nazi leaders on the human scale – as fathers, lovers and husbands – is what makes their activities more repellent than ever.

Jane Thynne's new novel A War of Flowers is published by Simon & Schuster on November 20