The beautiful, blonde-haired young woman stepped out of her car and walked slowly towards the English Garden in the German city of Munich. She'd come here often, but today she seemed distracted as she passed the familiar willow trees and the secluded glade where she had once sunbathed naked. Her blue eyes were blank, oblivious to the sun glistening on the river. She stopped, her heart thumping as she pulled a small pistol from her handbag. A single shot pierced the air and the woman slumped to the ground.

When Britain declared war on Germany in September 1939, Unity Mitford shot herself in the head. Obsessed with Adolf Hitler, the 25 year old had moved to Munich and stalked her hero until he befriended her, declaring she was "a perfect specimen of Aryan womanhood" and giving her an apartment recently "vacated" by Jews. When her homeland took action, she decided to end it all. But, in a tragic twist of fate, Unity did not die that day, the bullet remaining lodged in her head until she died of cerebral meningitis, aged 33, in 1948.

As compelling as Unity's tale is, she was just one of six sisters whose extraordinary lives made headlines around the world. There was the communist, the duchess, the novelist, the farmer and two fascists. Theirs is a tantalising tale of scandal, alcoholism, broken marriages, doomed affairs, heartache, tragedy and family feuds.

They were always going to be unique. Born into the British aristocracy, the Mitford girls - Nancy was the first born in November 1904, followed by Pamela, Diana, Unity, Jessica (aka Decca) and Deborah - had an eccentric childhood, along with their brother Tom. The children of David Bertram Ogilvy Freeman-Mitford, the 2nd Baron of Redesdale, and his wife, Sydney, they were brought up in Gloucestershire. Right from the start, their parents set about making the children free thinkers, insisting on home-schooling them in their grand yet impoverished country homes. David, aka Farve, had a fiery temper and used to "hunt" his daughters with bloodhounds as part of a family game, while "Muv" remained a distant character whom they rarely saw. They also passed on their political preferences - both parents were fascist supporters, but at the onset of World War II, David renounced his views. Sydney did not, leading to the end of their marriage.

Rules at home were unconventional, to say the least. Never forced to eat something they didn't like, Unity lived on nothing but mashed potato for two years. Windows had to be left open, even in winter, and formal education was banned as Farve thought playing hockey at school would fatten his daughters' ankles. To relieve the tedium of home life, the girls made up pet names for one another - Unity was known as "Bobo" and Diana was "Nardy" - and formed secret societies. "We either laughed so uproariously that it drove grown-ups mad, or else it was a frightful row which ended in one of us bouncing out of the room in floods of tears," recalled Deborah. Their intense relationship would continue throughout their lives, with the sisters' letters printed into collections and their adult altercations enthralling the public.

Played out over 104 years, the Mitford saga is now in its final chapters. Deborah, aged 88, is the last surviving sister.

NANCY: the novelist

Nancy was the first to fly the coop. An avid reader, she began to write for UK society magazines The Lady, Vogue and Harper's Bazaar and used her quick wit to pen the novel Highland Fling in 1931, followed by Christmas Pudding in 1932. She became known as one of the "Bright Young Things" of the era.

For Nancy, a quiet life wasn't an option. She threw herself into high society, enthusing, "I'm just so rich I go first class everywhere." The only blot was her love life. When her engagement to closet gay Scottish aristocrat Hamish St Clair-Erskine ended, she attempted suicide at a friend's home by switching on a gas fire without lighting it. "It is a lovely sensation," she wrote, "just like taking anaesthetic." Suddenly concerned that her pregnant hostess might miscarry on discovering her corpse, she "got back to bed and was sick". In 1933, Nancy wed Peter Rodd, but the marriage was a failure thanks to his philandering ways and lack of financial know-how, and Nancy's infertility due to an ectopic pregnancy. They divorced in 1958.

Although her romantic life was a mess, Nancy's novels were going from strength to strength, with the critically acclaimed and best-selling semi-autobiographical The Pursuit Of Love and Love In A Cold Climate, published in 1945 and 1949 respectively. The books recount Nancy's life through the fictional Radlett family and include the character Fabrice de Sauveterre - in real life, Nancy's lover Gaston Palewski. The charming Palewski, whom she had met in London, was a member of the French resistance and right-hand man to French president Charles de Gaulle.

The relationship was heavily one-sided and "the Colonel", as she called him, would never commit to her, despite her pleading, "I wish I were sitting on your doorstep like a faithful dog waiting for you to wake up." Undeterred, she moved to Paris to be near him after World War II, and discovered instead a fabulous new lifestyle with an elegant apartment and Christian Dior clothes. "I feel so wonderful l don't know it's me," she wrote. Nancy, aged 68, died of Hodgkin's disease in 1973.

PAMELA: the farmer

Born in 1907 and known as "the quiet sister", Pamela eschewed the advances of contemporary poet John Betjeman - he referred to her as the "rural Mitford" - and headed to the country to farm family land. She married and divorced scientist Derek Jackson, then lived the rest of her life with Italian horsewoman Giuditta Tommasi, who died in 1993. Pamela passed away the following year.

DIANA: the fascist

Diana was the first sister down the aisle. Described by one male friend as "the most flawlessly beautiful woman I have seen", her marriage to brewing dynasty heir Bryan Guinness in 1929 was the society wedding of the year. She bore two sons, Jonathan and Desmond, and devoted herself to hosting legendary parties. Evelyn Waugh even dedicated his novel Vile Bodies, a satirical take on decadent young London, to the couple. And yet, just three years later, Diana would be involved in the biggest society scandal of the time.

To the horror of family and friends, she began an affair with Sir Oswald Mosley, a married womaniser and soon to be founder of the British Union of Fascists (BUF). She was besotted: "He had every gift, being handsome, generous, intelligent, and full of wonderful gaiety and joie de vivre," she gushed. He also had a wife and children whom he refused to leave, but Diana became his mistress, even turning a blind eye when, on his wife's death, he began an affair with his sister-in-law. When Mosley launched his extremist political party, with its militaristic uniform and anti-Semitic rallies, he became the black sheep of British politics and was labelled the most hated man in England. Banned from the family home and frozen out by her society friends, Diana was unrepentant: "I followed him, politically, absolutely blindly."

Like Unity, Diana was enthralled by Hitler. She had several private meetings with the dictator on BUF business and secretly married Mosley in Joseph Goebbels's apartment, with Hitler as guest of honour. She allegedly had a diamond swastika in her jewellery collection and once admitted, "I am not fond of Jews," suggesting they all go and live in Uganda.

"Anyone but a moron would have loved the opportunity to talk in private to Hitler," she wrote in her autobiography, A Life Of Contrasts, in 1977. "Nothing would ever make me pretend I was sorry to have had this unique experience."

Diana and Mosley's connections hadn't gone unnoticed, with MI5 documents noting, "Diana is said to be far cleverer and more dangerous than her husband, and will stick at nothing to achieve her ambitions."

In 1940, the pair were interned in separate prisons as Nazi sympathisers. Unbeknown to Diana, who would not discover the truth until 10 years after her sister's death, Nancy was the person who denounced her to the authorities. "Not very sisterly behaviour, but in such times I think it one's duty," Nancy later confessed to a friend. Although Diana and Nancy maintained a tentative friendship, it was too much for Decca who, as an ardent socialist, could never bridge the gap between her own and Diana's political differences, and refused any attempt at reconciliation with her. "I could not have borne it," insisted Decca.

At the end of 1941, British prime minister Winston Churchill intervened to allow Diana and Mosley to live together in a cottage in the grounds of the all-female Holloway prison. Diana's devotion to her husband never waned, saying, "It's rather incredible to be locked up like that with somebody for two years and we hardly ever quarrelled."

After their 1943 release, which was met with mass public protest and an indignant letter from Decca to Churchill, the couple were kept under house arrest for the remainder of the war before moving to Ireland, then Paris. Diana edited a fascist magazine and wrote a biography of her friend Wallis Simpson, the wife of the Duke of Windsor and the woman for whom he abdicated the throne. Diana remained a fascist to the end, although her opinion of Hitler was tempered in later years, writing in A Life Of Contrasts, "I didn't love Hitler any more than I did Winston." Her love for Mosley, however, remained true until his death in 1980 and her own in 2003, aged 93.

UNITY: the Hitler confidante

Unity was conceived, prophetically, in a Canadian town called Swastika and was transfixed by Hitler. In 1933, when Diana travelled to Germany for the Nazi's first Nuremberg rally, she took 18-year-old Unity with her. It was the start of a chilling obsession with the man she would teasingly refer to as "Wolf". Allowed to take a German language course in Munich, she scanned his movements in newspapers and staked out his favourite restaurant until he finally noticed the pale-skinned Englishwoman and invited her to join him.

Fascinated by her interest, Hitler allowed Unity to join his inner circle, and when Deborah visited her sister and saw them together she remarked, "Bobo was like someone transformed when she was with him. She was shaking so much she could hardly walk." Unity also wrote a letter to Nazi newspaper Der Stürmer, confirming her allegiance as a fascist and ending with, "PS: please publish my name in full. I want everyone to know that I am a Jew hater." When her year of study ended, she remained in Munich, staying in a flat that Hitler found for her in 1938 - "It belongs to a young Jewish couple who are going abroad," she chillingly wrote - and continued her association with the Führer. Of one of her frequent visits to his home, she told a friend, "The greatest moment in my life was sitting at Hitler's feet and having him stroke my hair."

In 2007, allegations emerged that Unity's relationship with Hitler had run deeper than anyone suspected, when witnesses from an Oxfordshire maternity home reported a young Unity had given birth to a boy fathered by Hitler. It sparked a media frenzy in the UK; Deborah disputed the claims as nonsense.

JESSICA: the communist

Decca's politics had always swung to the left and she pursued her passion in a dramatically polar manner to her sisters. Falling in love with Winston Churchill's nephew Esmond Romilly, who'd just returned from fighting the fascists in the Spanish Civil War, the pair ran away to Spain and married. Their families were furious - Decca's father disinherited her - but the unrepentant couple settled in London's East End, where she gave birth to a daughter, Julia, who sadly died of measles at four months.

In 1939, Jessica and Romilly moved to the US, where she was welcomed into New York society as "the wife of Winston Churchill's nephew". She gave birth to Constancia, aka Dinky, in February 1941. That November, Romilly, who had enlisted in the Royal Canadian Air Force, went missing in action. He was never seen again. Grief-stricken, Decca moved to San Francisco, where she married lawyer Robert Treuhaft in 1943, and had two sons, Nicholas and Benjamin. Once again, tragedy struck when Nicholas was killed in a road accident.

Decca became an active civil rights worker during the '50s and '60s, and got caught in a riot when a Martin Luther King Jr rally was attacked by the Ku Klux Klan. She and Robert joined the Communist Party USA and became targets of Senator Joseph McCarthy's House Un-American Activities Committee. In 1960, family grudges resurfaced when Decca's memoirs, Hons And Rebels, was published. Although Nancy told her it was "awfully good", she complained that Decca "has quite unconsciously copied from my book instead of real life". But Decca's witty memories of Mitford life transformed her into an acclaimed writer and she found work as an investigative journalist, making The New York Times bestseller list with her exposés. She died of cancer in 1996, aged 78.

DEBORAH: the duchess

Deborah's love life took a more conventional route than that of her sisters. In 1941, she married Andrew Cavendish, 11th Duke of Devonshire, and the now Duchess of Devonshire became mistress of Chatsworth, which she turned into Britain's most successful stately home - and location for the 2005 movie Pride & Prejudice. Last year, in an interview with the UK's Daily Telegraph newspaper, she spoke of having tea with Hitler during a visit to Munich with Unity and their mother in 1937. Asked by the reporter if she would have preferred to have tea with her idol Elvis Presley or Hitler, she responded, "Elvis, of course! What an extraordinary question."

Although the 88-year-old widow no longer has any sisters to write to, she adds, "I still go on writing to Diana in my head because she is the person I had a particular affinity with." She's amazed that interest in the Mitfords has never ceased. Why that is, she muses, "I cannot imagine, although I can now see things worked out rather differently for us all."