HE is the descendant of one of the most infamous and intriguing aristocratic families of the 20th century - the prototype "Bright Young Things" who lit up the world of British literature and politics on one hand and shocked the nation thanks to a dark flirtation with Nazism on the other.

But recently he has been living in a tent on Portobello beach in Edinburgh along with his most prized possession - an upright piano.

But then given that Ben Treuhaft is a scion of the Mitford sisters, few would expect him to ever live a normal life.

The 66-year-old piano tuner is the son of Jessica Mitford, one of the infamous Mitford sisters, who once filled the gossip pages of the 1930s. And he counts a one-time aristocratic groupie of Adolf Hitler, the wife of notorious British fascist leader Oswald Mosley, and one of the best female novelists of the last 100 years among his aunts.

Treuhaft set up his camp on Portobello beach - including hiring professional movers to transport his 550lb piano - after he was kicked out of home by his wife.

He has since moved in with his girlfriend, after intervention from the city council, as it is illegal to camp on the beach, but his tent remains on the sand.

Treuhaft spent his childhood hearing stories from his mother, one of the most prominent members of one of the most complex, contradictory and fascinating families of the last century. Jessica was a communist, and he grew up as the child of "huge reds" during the era of Joseph McCarthy-inspired communist witch-hunts in Cold War America. By the time Treuhaft was born in 1947, Jessica had emigrated to California and married Jewish lawyer and civil rights activist Robert Treuhaft.

Expected to marry within a well-connected world of wealth and live a life of luxury, the sisters were drawn to political extremes in an age of revolution.

While two of the six sisters, Unity and Diana, became besotted with the far right, Jessica etched a hammer and sickle on to her bedroom window with a diamond ring. She ran off to Spain with socialist Esmond Romilly, who would die in the Second World War, using cash from a bank account which she had saved throughout her childhood. The royalties from the books she would go on to write are paid into the same account to this day.

Ben said: "My mother knew from an early age that she wanted to run away from the privileged world. She saved all the money from the projects that children do to make money. She had £50 by the time she ran off to Spain."

While Jessica was drawn to the Left, Unity - whose middle name was Valkyrie - set off for Nazi Germany in the mid-1930s. Eventually catching the eye of Hitler and succeeding in her quest to enter his inner circle, she became "Hitler's English girlfriend".

When Ben was born, Unity was slowly dying from a bullet lodged in her head. It was a self-administered gunshot wound that left her "a changed person", according to her family.

She shot herself on the outbreak of war, devastated that Germany and Britain were about in a state of conflict. She was flown home to England as an invalid and died in hospital in Oban in 1948.

Meanwhile, Diana had married Oswald Mosley - founder of the British Union of Fascists - at Joseph Goebbels's home in Berlin in 1936, with Hitler as a guest. She was later interned in a house in the grounds of Holloway Prison along with her husband due to their fascist sympathies. She never renounced her politics or affection for Hitler, and died in 2003.

Ben's other aunt, Nancy Mitford, wrote acclaimed novels including the classic Love In A Cold Climate. Treuhaft's mother herself became a famous investigative journalist in America.

Of his infamous fascist aunts, Treuhaft said: "The one that was Hitler's best pal, Unity, was my mother's best pal throughout everything. She loved her unconditionally, they had painful times but she always called her Bobo.

"After she shot herself and was dying over several years, it was an extremely hard period for my mum. Communists weren't allowed to travel from the United States then so she wasn't able to see her.

"But Diana was hated by my mother without any let-up. When I was a kid she said it would be nice to meet me. My mother said it's very nice of you to offer but she wouldn't want me coming back as a lampshade. [There were rumours Germans had made lampshades out of the skin of Jews during the Second World War]. I never met her, my mum wouldn't let me. But I don't regret that, it wouldn't have been much fun to hang about her."

As he grew up, Jessica would become a famous journalist. Her work The American Way Of Death, a 1963 exposé of the funeral industry, became a best-seller. However, according to Treuhaft, his father made a major contribution: "He wrote at least half of that stuff. It wasn't acknowledged as the publisher thought the Mitford name would sell."

It was while she was working on her 1960 autobiography, Hons And Rebels, while in the south of France that Treuhaft recalls one of the most enduring memories of his mother - although its xenophobia is wince-enducing.

He said: "It must have been about 1958. She took me to this big gourmet French restaurant and we were at a table near these German folks. In this big, loud voice she says, 'There's some disgusting, beefy, redneck Germans, I don't know why they let them in this place.' I was crouching down, saying, 'Mum, they're not beefy redneck krauts, they're just Germans having their lunch', but she kept going after them.

"That's how she was, very opinionated, and she hated them on sight. I suppose she knew what a fascist was and could probably spot them a mile off."

Jessica "ate up" ostracism and "loved having enemies", according to Treuhaft - not a bad quality for a member of the Communist Party in 1950s America. Both his parents were called before the House Committee on Un-American Activities while he was a child.

"I didn't know what a communist was, but I had to go around being one and defend her," Treuhaft said. "My school was very anti-communist, as the whole country was. It was really embarrassing to be a communist kid."

Given the strength of his mother's personality, it is perhaps not surprising that they fell out while Ben was in his twenties. However, they reconciled and he described spending a wonderful decade with her before her death in 1996.

Keen to carve out his own identity, Ben became a piano tuner in the 1970s, working in some of the world's most famous venues for renowned musicians including Vladimir Horowitz and Glenn Gould. The work took him from California to New York to Tokyo, before he moved to Edinburgh, bringing his piano-tuning business with him, last year.

It has allowed him to be close to the surviving Mitford sister, Deborah, now the Duchess of Devonshire after her marriage to Lord Andrew Cavendish. Their granddaughter, Scottish model Stella Tennant, is also a relative of Treuhaft. He is planning a visit to his aunt to celebrate her 94th birthday.

While, like his mother, Treuhaft has a taste for adventure, it appears he is now planning to put down roots in Scotland's capital. The Mitford descendant has even started volunteering at a Leith charity shop now.

"I think I'm going to stay in Edinburgh," he said. "I love Scotland more than anything. The charity shop is great - they're all commies there."