She is the widow of the founder of the British Union of Fascists, and the former confidant of Adolf Hitler. Now living in contented, self-imposed exile in Paris, she was incarcerated 60 years ago for her far right-wing political views. But, after spending her adult life outraging public opinion, Lady Diana Mosley again confounds expectation: she does not like Jean-Marie Le Pen.
On the face of it, it is a surprising judgement. In Belgium and Austria, far-right politicians (those you might imagine to be her natural allies) have luxuriated in Le Pen’s presidential surge. This side of the channel, mainstream parties fear the succour his success will give to the British National Party. Yet Lady Diana is unimpressed.
Some might suspect a certain amount of snobbery in her judgement - she is, after all, the daughter of the second Lord Redesdale - but, no, hers is an ideological stance. Like her late, zealously patriotic husband, Sir Oswald, she decided at the end of the Second World War that the loss of Britain’s empire was inevitable; its future could not lie in the kind of isolationism promoted by the French National Front.
Now 91, she holds fast to her opinion. "I’ve had a look at Le Pen’s programme," she confides from her Paris apartment. "He is just a crusty old Eurosceptic Tory backbencher, everything I most dislike. In all essentials, and in particular with respect to Europe, his views are the opposite of mine. Mosley was a dedicated European and could never have got together with Le Pen."
But, she says: "I don’t think his success is a very bad thing. I suppose it was time for something to happen, politics had begun to bore the French."
For believers of Lady Diana’s stamp, the parvenus of fascism have nothing on the great master. Power, she concedes, can be a great aphrodisiac, and - without alluding to her own feelings - she adds, "All of Germany was ‘in love’ with Hitler.
"He had beautiful manners and it is always interesting to talk to a man with such an enormous potential influence on events." In this respect - though she admits she has never met him - Le Pen is simply overshadowed. "I am sure he has very little of the power to charm to which you allude," she says. By common consent, Lady Diana Mosley is as striking in old age as she was beautiful as an 18-year-old debutante.
The third of the six celebrated Mitford sisters (there was a brother, Tom), she is the great survivor of the clan, the colourful, eccentric family which has generated a library of novels and non-fiction and a mountain of newsprint.
It was an extraordinary upbringing, recounted in her recently republished autobiography, A Life of Contrasts. Lady Diana likes to make her readers laugh. She has, for example, tales of her father (known to his offspring as "Farve") who, despite his antipathy to the written word, was obliged as a young man - like one of PG Wodehouse’s comic heroes - to take a job at upper crust magazine the Lady. There he amused himself by chasing rats around the building, in company with his pet mongoose.
Or consider Uncle George, who took revenge on a supposed slight on the family name by Sir Edmund Gosse, by composing an epitaph for his foe: "Here lies Gosse/No great loss". "Uncle George made the couplet rhyme" writes Lady Diana, "while Farve pronounced loss to rhyme with horse, as we all did, which rather spoiled the joke."
Clever and competitive, the older Mitford girls reached maturity with the "Bright Young Things", the self-consciously rich and risqu group so beloved of the gossip columnists of the early Thirties.
"Our social life was far from ‘wild’," Lady Diana says now. " I was very fond of my friends and we had parties, but with Evelyn Waugh, we laughed about Bright Young People, and never considered ourselves to be part of them."
For his part, the novelist was infatuated with Lady Diana, dedicating Vile Bodies to her and her husband, Bryan Guinness. That the object of his affection was already carrying her first child only nourished his passion.
"Do you share my admiration for Diana?" he wrote to the novelist Henry Yorke. "She seems to me the one encouraging figure in this generation - particularly now she is pregnant - a great germinating vat of potentiality, like the vats I saw at their distillery."
But her relationship with Waugh would rapidly deteriorate - "he became rude and morose because he drank too much" - and she quickly lost other friends. Lytton Strachey died suddenly; Dora Carrington committed suicide. There was a void in her life, filled after a chance meeting at a party, by Sir Oswald Mosley. With her taste for the extreme, she was immediately drawn to this charismatic, maverick politico; he was smitten by her beauty.
The two began a love affair, but it was clear from the outset Mosley had no intention of leaving his wife, Cimmie. Instead, Lady Diana took a house in London’s Eaton Square to smooth the progress of their passion, though inevitably the newspapers were scandalised. Yet, she says, she felt no sense of stigma. "Probably there were people who disapproved of me, but I had so many friends it never mattered."
But if many of those closest to her forgave her sins, Lady Diana too had to extend her tolerance to her partner. Mosley was a serial adulterer. To Cimmie, he had confessed to a succession of affairs and even after his wife’s death in 1933 he continued his liaison with Baba, her sister.
This was of no importance to Lady Diana. "As I always knew Mosley was by nature a philanderer, I was not surprised by his infidelities," she says. "Looking back, our marriage was perfect."
Nowadays, she agrees with the assessment that she had become bored with Bryan and was glutted with the easy hedonism of social life. In choosing Mosley and fascism, she was reacting against frivolity by choosing a seriousness of purpose. It was a route which led to her estrangement from her sister Jessica (the two never spoke after the Munich agreement) and when war eventually came, her behaviour was proof for George Orwell that the potential traitors in Britain were the rich.
Yet, encouraged by Mosley, her fascination with Nazi Germany grew. True, it wasn’t her, but younger sister Unity who motored the English shires with swastika pennants flying from her car before transplanting to Bavaria to hang out in Hitler’s favourite restaurants. Nevertheless, Lady Diana seemed as keen to penetrate the Nazi inner circle. She watched the first Nuremberg rally, returning to Germany in 1935 after Unity had written to tell her she had met the Fhrer. Then, while her younger sister courted the goose-stepping "storms" (as Unity affectionately called them), Lady Diana established an intellectual rapport with Hitler which developed into friendship.
She has keepsakes of her brush with power. She and Mosley were married 65 years ago in Goebbels’s drawing room. As a present, the Fhrer inscribed a photograph in a silver frame. Goebbels gave a set of books, which remain in the library of Lady Diana’s Paris apartment. She says: "I have no mementos, except the 20 volumes of Goethe’s works, which I am now unfortunately too blind to read, because they are in German print."
But for all her empathy with the Nazi regime, she was unaware of the fate of the Jews until the horrific truth was revealed to the world at the end of the war from beyond the gates of Belsen.
"I deplore bullying of any kind and I deplored the murders," she says. "To me, war itself is the greatest atrocity, which engenders all atrocities. I blame Hitler most of all for starting the war.
"I never heard him mention the Jews. Of course, I knew about the Nuremberg Laws, which I suppose he hoped would induce the Jews to leave Germany. The whole thing was an appalling tragedy, and the war nearly wrecked Europe."
Yet, if she was ignorant of the worst of a barbaric regime, as late as July 1939 she was in conference with Hitler and had planned another visit to Munich when war intervened.
The following summer, in Britain, both she and Mosley were imprisoned, and - leaving her ten-week old son behind - Lady Diana was sent to Holloway. It took 18 months and the personal intervention of "Cousin Winston" Churchill to allow Lady Diana and her husband to be together, first in prison accommodation and then under house arrest.
After the war, there was a wandering exile through some of Europe’s most well-upholstered refuges (she befriended the Duke and Duchess of Windsor at Orsay in France). In 1959, Mosley stood for election in North Kensington, a constituency where black immigrants had replaced Jews in his British supporters’ programme. "We opposed unrestricted immigration," Lady Diana emphasises now. "Each country must decide how many immigrants it can absorb, and restrict immigration accordingly. This is recognised everywhere."
But her opinions are still reviled. Reviewing one of her biographers, the historian David Cannadine wrote: "This book is tolerant, fair-minded and generous, which is substantially more than can be said for its subject."
Such criticism, you suspect, has always left her unmoved. Lady Diana’s husband died 21 years ago, her beloved sister Nancy in 1973. The obvious sadness of old age, she says, is the loss of those you love. Yet she "devours" books (she can manage Latin print) and has "as many friends as I have the energy to see".
She adds: "I am lucky enough to be well, to have wonderful sons and grandchildren." Her nephews and nieces likewise adore their "Aunt Honks".
And she can take stock of the world around her. England, she perceives, is in decline. "Nothing seems to work very well, but great people have their ups and downs and I have faith in the English, they will stage a recovery."
But it is surely ironic, after she was imprisoned for her politics two generations ago, that Lady Mosley should now look askance at the fascists on her doorstep. But in her way, she does.
"Of course it is very sad for someone of my generation to see the decline of our country to what it has now become. I put my faith in Europe, which, if it were united, could still save the world as the most civilised continent."
It is her way of proffering a polite ‘Non’ to Le Pen; or, in Mitford speak, "Be orf with you."
A Life of Contrasts, by Diana Mosley, is published by Gibson Square Books, 10.99.