While they live in what some have called the Golden Age of Biography, contemporary biographers on the prowl for new subjects don't have it as easy as we might expect. Finding fresh, interesting biographical subjects whose lives are tied intimately to the greater historical vicissitudes of their times is not, one suspects, an easy task. The obvious choices--Churchill, Hemingway or Nixon, for example--have already received sustained attention, and to avoid writing revisionist tracts in their large bibliographical shadows (or finding new angles on their success, as Stacy Schiff did with Véra (Mrs. Vladimir Nabokov)), biographers are forced to root out subjects who might not come readily to mind.

Like, for example, Diana Mosley.

In the heyday of fascism, Diana Mosley was vilified by many in her native England and encouraged by others. No matter which side you were on, though, you knew who she was. Today, though she's still living (she turned ninety last month), her name has slipped from the common parlance. But as Jan Dalley resoundingly shows her in new biography of Diana, she meets the biographer's greatest demands: she came from an interesting, even eccentric family with a long history, and as an adult she managed to get caught up in and even influence her era's direction.

Diana Freeman-Mitford was the fourth of seven children in a family that produced more than its share of celebrated figures. The eldest daughter, Nancy, became a bestselling comic novelist (The Pursuit of Love is her best-known work today); Jessica became a Communist and later a journalist and civil rights activist in America (she wrote The American Way of Death); Unity became a Nazi and a member of Hitler's close circle; and Deborah (the youngest sister in the family, she is now the Duchess of Devonshire) writes popular books about her house and the family history.

By any measure, they made a complicated, eccentric family. The father, Lord David Redesdale, was an avid sportsman, and his children claimed he read only one book (Jack London's White Fang) and found it good enough to feel no need to read another. The mother was more interested in the children's education, but she was by all accounts rather distant and cold to them. Their house had a large, well-selected library, though (Lord Redesdale consulted his children on which titles to keep when he was selling off a good chunk of an inherited collection), and a surprisingly impressive array of visitors made their way to the Mitford house. Indeed, by the time she was a teenager, Diana was enjoying rarified company: Winston Churchill, Harold Acton and Evelyn Waugh were among the family's visitors and friends. (Lord Redesdale found his daughters' younger friends unappealing, though, and called them collectively the "sewers.")

But it was Diana's marriage (at eighteen) to Bryan Guinness, whose father was the Minister of Agriculture and the director of the Guinness Brewery, that seemed to solidify her position in the upper class after spending her childhood careening from one financial setback to the next. (Her father fancied himself a builder and spared no expense when he built the family's much-maligned house, Swinbrook.) Guinness, Diana thought, was gratifyingly like her and, perhaps more importantly, unlike her father. ("I know you will like him," she wrote to a friend, "because he is too angelic and quiet and not rough and loathes shooting, and loves travelling and all the things I love.") A period of whirlwind, Twenties-style decadent socializing followed their marriage, as did two children. But then Diana, just weeks shy of her twenty-second birthday, spent an evening dancing with Sir Oswald Mosley (a "maverick politician, socialite and notorious womanizer," as Dalley puts it succinctly; his famous motto for political versus sexual strategy was "Vote Labour; sleep Tory"). "He was older than she," Dalley writes,

--thirty-five to her twenty-one at the time they met--and well known in both politics and society. He was a dashing figure: handsome in the Rudolph Valentino style then in fashion, elegant, witty and very charming to women. He had fought bravely in the First World War and entered politics very young; he had had great political acclaim in the Conservative Party and the Labour Party, had left the latter to found the New Party, which had quickly foundered; in 1932 he was working to launch the British Union of Fascists. He was an idealist and a brilliant talker: Diana fell in love with the man, and with his political passion and certainty, at the same time.

Though, like Diana, Mosley was married with children, they began a poorly concealed affair that, a few years after the death of Mosley's wife and Diana's divorce from Guinness, finally ended in marriage. And in a very real sense, meeting Mosley seems to have ended the Roaring Twenties for Diana and brought her, just as the world shifted in the same direction, to the fascism that dominated the 1930s:

She had aspired to the life she had with Bryan, but its rich diet had soon turned her stomach and she wanted something bigger, darker, more purposeful and more dangerous. Glutted with the easy hedonism of social life, Diana was attracted by its opposite. Most people rebel from the workaday aspects of life towards the more light-hearted; in choosing Mosley and fascism, Diana rebelled away from the frivolity of her socializing life into "seriousness of purpose."

Although Mosley had developed an admiration for the German troops' "order, dignity and dedicated purpose" in the First World War, it was Diana who became a true Germanophile during the 1930s. (She wasn't the first one in her family--her grandfather was an outspoken Germanophile in the nineteenth century--nor was she the only one in her generation; Unity had already papered her bedroom walls with Nazi posters.) Indeed, it was Diana, and not Mosley (who favored the Italians and even accepted secret funds from Mussolini), who first approached the Nazis. After meeting Hitler's Foreign Press Secretary in the summer of 1933, Diana and Unity accepted his invitation to travel to Germany. Although they didn't meet the Führer on that trip, they did attend the Nazis' first Nuremberg rally. Diana, Dalley writes, "was deeply impressed," and she realized that Mosley would profit from "close links with the German high command."

Diana saw that the future in fascist terms might lie with Germany rather than Italy. Perhaps she had more sensitive political antennae than Mosley, who was introspective where Britain was concerned. She now set herself to learning German perfectly, to expanding her friendships among the Nazi élite and to launching a plan on which Mosley's political future might depend.

In time, Diana met Hitler through Unity, and they struck up a friendship that lasted four years. Unity, in turn, became an obsessed Hitler groupie (or perhaps, more appropriately, a Hitler stalker), with a tragic conclusion.

Ironically, Mosley himself only met Hitler twice. Just as Mosley favored Mussolini over the German brand of fascism, Hitler likewise apparently thought (correctly) that Mosley's fascist movement would fail in Britain. "In 1935," Dalley writes,

after Unity got to know Hitler, she wrote in a letter home to Diana that Hitler had said that Mosley was unwise to attempt to import the term "fascism" and to adopt the black shirt--both, Hitler thought, were "foreign," out of keeping with British traditions, and likely to impede Mosley's success. A successful political movement had to grow from deep national roots, Hitler believed, and, according to Diana, he always said that "National Socialism is not for export." He had a brilliant grasp of the mechanics of mass appeal, and knew how to conjure up the power of the past. When Unity asked him what he would have recommended for a British-based fascist movement, Hitler replied that Mosley should have referred back to an important national moment--namely, the revolution of Oliver Cromwell--and called his men "Ironsides."

Mosley's lack of chemistry with Hitler didn't keep him out of Germany altogether, though. Indeed, when Mosley and Diana were finally married in 1936, the service was conducted in Josef Goebbels's apartment, and Hitler himself attended. (His wedding present, Dalley notes, was "a large photograph of himself in a heavy silver frame topped by the double-headed German eagle.")

Hitler's attraction to Unity and Diana is an abiding mystery, as Dalley readily acknowledges. Their "perfect Aryan looks" and their high society connections must have appealed to him, but as Dalley points out, the differences in the two sisters' personalities shaped their relationship with Hitler in different ways.

Although Unity worshipped him to a degree that might have been embarrassing, she was completely unsexual in her adoration, and she made him laugh with her unabashed way of talking. Witnesses remembered how she could say things to him that nobody in Germany would have dared say....In Diana's case, the relationship was less close, but more intellectual. She was less of a fanatic, more informed about politics, and she did establish a relationship with Hitler that was independent of Unity's. She wanted to charm him, and she set about it with her usual success. If she was as breathlessly smitten as Unity, she hid it better and her attitude had less of the schoolgirl crush about it; after all, she had a Führer of her own at home.

Whatever the complex attractions might have been, Diana's friendship with Hitler ended just as the war began. On May 23, 1940--thirteen days after Churchill replaced Neville Chamberlain as Prime Minister--Mosley was arrested under Defense Regulation 18b, which had been quickly amended to allow the arrest of anyone belonging to an organization if "the persons in control of the organization have or have had associations with persons concerned in the government of, or sympathies with the system of government of, any Power with which His Majesty is at war." Other arrests followed--as Dalley notes, "In all, about 800 British Union members and sympathizers--700 men, 100 women--were interned in the summer of 1940, in prisons at Brixton, Holloway and Liverpool (where conditions were worst), as well as at the specially created camp on the Isle of Man." And on June 29th, despite her having a newborn infant, Diana herself was arrested (as Mosley's wife, she was considered a danger to the state; even her sister Nancy secretly campaigned for Diana's arrest).

The Mosleys remained in prison until November 1943, when they were released on medical grounds (they were both, not surprisingly, in poor health because of the prison conditions).

In the end, the war took a shocking toll on the Mitford family: in addition to Diana's imprisonment, Unity attempted suicide and died in 1948, and their brother Tom volunteered in 1945 for a quasi-suicidal transfer to Burma rather than fight against Germans; he died from a gunshot wound just before the war ended.

Oswald Mosley died in 1980, but Dalley was able to interview Diana for several years to prepare her biography, and the long work that Dalley devoted to her subject shows. Diana Mosley is a serious, well-researched and compelling biography. On a personal level, it certainly expands our understanding of the Mitford family. But it's far more powerful as a cultural history of a remarkably diverse period, from the hedonistic 1920s through fascism's heyday in the 1930s and the worldwide reckoning that followed. And Diana seems to be the perfect biographical subject for such a history. (As Dalley points out, "Diana was one of very few people who knew both Churchill and Hitler well.") Indeed, once Diana meets Mosley and the focus shifts from the individual to far larger subjects, Dalley's text becomes downright fascinating.