The wife of the UK's leading fascist and a staunch friend of Hitler, Diana Mosley confided her secrets on condition they would not be aired in her lifetime. Now, following her death in August, her extraordinary life has been laid bare.
Friend of fascism: Diana, second left, at a Nuremberg Rally in 1936
Published in 1977, Diana Mosley's autobiography presents a highly selective account of a highly controversial life. There was much she wanted to hide.
It took the veteran journalist Anne de Courcy to peel off the layers of concealment in which this British aristocrat had enveloped her life.
Speaking to BBC News Online, de Courcy, who became her official biographer, reveals an enlightening exchange between the two women.
"One day when I was talking to her, I noticed she looked a tiny bit uneasy," de Courcy says.
"I found myself saying, 'Diana, would you rather this was not published in your lifetime?' And with an air of great relief, 'Oh, I really would, that would make me much happier.' From then on she talked much more freely."
This understanding gave de Courcy exclusive access to Diana's correspondence as well as her memories, shining light on her associations with the likes of Evelyn Waugh and casting a glittering party veneer over the ominous gloom of the 1930s.
Mosley's death in August finally lifted this self-imposed embargo and de Courcy's book hits the shops this month.
"What I hoped [to accomplish] was to create a really intimate, personal portrait of this woman and her life, this woman who had known this monster, Hitler, so extremely well. To explain how, in spite of everything, how she became such a friend of his, and how she maintained this all her life," says de Courcy.
Flirting with fascism
The book gives a detailed account of Diana's flirtation with fascism.
Readers are treated to hitherto unpublished photographs of Diana among top Nazi brass, from her attendance of the first Nuremburg rally ("I can't possibly do without lipstick") to her marriage to Mosley in Berlin - at Joseph Goebbels' residence - in October 1936.
Diana Mosley (above, with Hitler) was born in 1910, one of six Mitford sisters
Among them were renowned socialite Nancy, fellow fascist sympathiser Unity, and communist activist Jessica
Only Deborah - the Duchess of Devonshire - is still alive
Hitler himself was one of the guests. His wedding gift: a framed photo of himself.
Diana Mosley was, of course, no ordinary errant Englishwoman. One of the famed Mitford sisters, she married Bryan Guinness, poet and heir to the brewing fortune, in 1929, aged 18.
Four years later, as the nation foundered in the midst of the Great Depression, she fell in love with Oswald Mosley, later the founder of the British Union of Fascists (BUF), for whom she left her husband.
It was on Mosley's behalf that she began travelling to Germany. Befriending Hitler, Goebbels and other members of the Nazi inner sanctum, Diana worked to help establish a BUF radio station in Germany, before war was declared in 1939.
Both she and Mosley were then imprisoned - Diana in Holloway - for the rest of the war, after which they moved to France for the duration of their lives.
De Courcy credits much of fascism's seductiveness for Diana with that of her paramour. Mosley was a hesitant entry into political life, and at first opposed thuggery for political ends.
Mosley never recanted her beliefs
She describes him as being drawn from the numbers of parliamentary democracy to the rule of one: "Originally he began as an independent conservative, then he crossed the floor of the house to the Labour Party," says de Courcy.
"He was a young man in a hurry. When the Labour Party wouldn't put his Mosley Memorandum through, he left it and founded the New Party, which was founded as something fairly left-wing, which was how he managed to draw a lot of his fellow Socialists over to him."
He gradually veered more and more towards fascism, first on the Italian model, with a uniformed force to quell unrest at meetings, and thence to correspondence with Nazi high command, German money flowing into BUF coffers, and numerous trips to Germany itself.
So did Diana ever condemn Hitler's atrocities?
"I pressed her and pressed her, and said, Hitler did do these terrible things, he brought about the Holocaust.
"Her reply was that the Holocaust was murder, all murder is wicked. She was categorical about that. She also said, 'The man I knew could not have done that. Perhaps he went a little mad'."
Diana Mosley, by Anne de Courcy, is published by Chatto and Windus. (William Morrow in the US.)