The Mitford family evokes a curious response in Britain, where it seems impossible to view members of the clan as other than loveable - if occasionally rather naughty - representatives of a decadent and decorative upper class. Because Nancy Mitford lightly disguised her parents and siblings in a series of amusing novels, it is these characters who now seem to have the greater reality. This is obviously to the advantage of the Mitfords, since some of them were far less charming than their fictional selves and were much more concerned with preserving their own pampered status quo.
Where Diana Mitford is concerned, the problem of establishing a clear image becomes particularly acute as she has always chosen to keep a great deal of herself in the shadows. There are a certain number of unassailable facts: she was a woman of enormous beauty who married first Bryan Guinness (the Hon Desmond Guinness is their son) and then Sir Oswald Mosley. She was an unwaveringly loyal supporter of her second husband, leader of the British Union of Fascists, and as a result was sent to Holloway prison for much of the second World War. She knew Hitler very well and, together with her inaptly-named sister, Unity, attended a number of Nazi rallies as a privileged guest.
Thereafter, trying to understand what might have been the motivating forces in Diana Mosley's life becomes an almost impossible task. Was she naive or was she indifferent to politics even when they intruded directly into her life? Certainly, Jan Dalley is no more successful than anyone else at getting behind the carefully-maintained maquillage of tranquillity that Diana Mosley consistently presented to the outside world. Cyril Connolly once described her beauty as "cow-like" and it is an apt term to use, given her air of placid calm under all circumstances. Even the worst trials she faced were not permitted to cause any disturbance; having been released from jail, she insisted in talking of her time there in almost childlike language - "darling, it was terrible at first, so damp and horrid."
Rather like the infamous description of the first World War by a survivor of the trenches ("My dear, the noise - and the people"), this devotion to ironic understatement suggests a refusal to engage with the world. It would also explain how Diana Mosley could take tea with the Fuhrer without troubling herself about his political opinions and their application. There is only one instance recorded of her mask slipping, and surprisingly, given Jan Dalley's heavy dependence on secondary sources, it would appear to have escaped the biographer's notice. In his autobiography, Second Son, David Herbert recalls sitting after the war on the Moroccan shoreline with Diana Mosley when she unexpectedly burst into tears and "seemed frightened and pathetic and bewildered" as she spoke of her husband's renewed interest in active politics and the trouble this might cause. But, as Herbert notes, when he next met her, she once more gave the impression that nothing and nobody could disturb her equilibrium.
Possibly this was truly the case and the distraught woman he had encountered in Morocco was a momentary aberration. The most obvious explanation behind all her actions after she met Oswald Mosley at the age of 22 is that they were inspired by love. If Diana Mosley had steeled herself to show a self-assured facade at all times, this was because her husband gave her no other option. After she left Bryan Guinness in 1932, she became Mosley's mistress, sharing him with the sister of his first wife and, very likely, a number of other women also. An incorrigible philanderer, Mosley only married her in 1936 - the secret ceremony took place in Berlin with Hitler one of the handful of witnesses - and he continued to have affairs thereafter. For a woman as much in love with her spouse as Diana Mosley, this behaviour must have been excruciatingly painful, but she never complained about her circumstances to anyone. Indeed, she was an unfailingly loyal and supportive wife even after Mosley began to articulate violently anti-Semitic views, although she also remained close to Unity Mitford, who in 1935 wrote to a German newspaper: "I want everyone to know that I am a Jew hater."
Despite what was presumably considerable research, Jan Dalley has been no more successful than anyone else in getting to know her subject. The greatest achievement of Diana Mosley has been to elude all efforts to capture her, even though she published her autobiography more than 20 years ago. Denied access to Diana Mosley's diaries and letters, as well as those of her late husband, Jan Dalley remains an outsider, pressing her face against the window and hoping to catch a glimpse of the person within. She fails: Diana Mosley remains as mysterious as ever.
Robert O'Byrne is an Irish Times journalist