The party boy charmer

So Dan, is it true you're the reason Kate Moss and Jade Jagger aren't friends any more? Dan Macmillan splutters for a minute, flicks his cigarette out of the window and says, quite unconvincingly: "They are friends." Really? "Yes. I don't know of any problem between them."

Macmillan, 29, is perhaps best known as the man over whom Kate Moss and Jade Jagger - who dubbed him "the vulgar viscount" - supposedly fought. According to tabloid lore, Macmillan two-timed Jagger with Moss (although there have been lurid insinuations of the closeness of the threesome). Jagger finished with him in a blazing row on New Year's Eve 2000. A few months later, so did Moss.

When Moss gave birth to her daughter Lila, Jade apparently sent her a necklace bearing the word "Slag". Wasn't Dan the problem? "Do I look like a problem?" he says with a cheeky smile that shows his gold tooth.

He doesn't. He looks deceptively sweet and vulnerable. Dressed in his own designs (a purple T-shirt with "Zoltar", the name of his label, across the front, a chunky gold necklace and a pair of low-slung jeans with funny zips on the back), his hair forming scruffy rats' tails as he twirls it around his finger, he looks every inch the bohemian artist.

We meet in his studio, a white warehouse-style space in a little yard in the heart of Soho. I'm here to look at his latest fashion collection, but his reputation as a wild, hedonistic aristocrat is far more appealing. Yet with his slight build, street urchin face and his gentle voice, the effect seems altogether effeminate.

Macmillan, the artist formally known as Viscount Macmillan of Ovenden, is the great-grandson of former Tory prime minister-Harold and heir to an earldom and a £300 million publishing fortune (he received £30 million from his trust fund on his 25th birthday). His greatgrandfather once bounced him on his knee and said: "Jolly little fellow, aren't you?" If the stories about him are to believed, he is certainly very jolly indeed.

He has a reputation for partying, debauchery and dalliances with beautiful women. Tales of wild orgies at his penthouse in Vauxhall abound. He laughs. "I don't have them," he insists. "My neighbour read some article where it was mentioned and said: 'I've never heard any parties going on, but why wasn't I invited?'

"I don't even go to parties that much now. I've got different priorities. I care about my work, I've got a girlfriend. Anyone who lives in a city in their twenties has a bit of a wild time, but you grow up."

So what are his vices? Cocaine, heroin, supermodels?

"Erm, San Pellegrino," he says after a pause. It might be true - I've just seen him drink three bottles of the sparkling mineral water - but it's not very rock 'n' roll. "No, not really," admits Macmillan.

He has been with his girlfriend, 21-year-old Stella Schnabel, the art-dealer daughter of American artist Julian Schnabel, for nearly two years. Has she been a calming influence? "Yes, a bit," he says.

Is he ready to settle down and start the next Macmillan generation? He will only say: "I'm really looking forward to having children. I looked after Jade's kids [she has two young daughters, Amber and Assisi] for years. That was nice."

Does he still see Jade and the children? "Now and then. We move in different circles but we still keep in touch."

He grew up at Birch Grove, set in 700 acres of Sussex countryside. His parents are now divorced. His great-grandfather doted on him and young Dan often attended dinner parties where guests included "all sorts of interesting people - politicians and artists". Once, he poured gravy on Margaret Thatcher's pudding, thinking it was chocolate sauce.

At Eton, he seems to be remembered primarily for his relish in dressing up for the school plays, particularly if he had to play a girl.

There was no pressure to go into the family publishing business. Just as well, because from an early age (he won a competition for a drawing of a robot at the age of six), art was what he wanted to do. He is dyslexic and thinks this might have something to do with it.

He studied at Central St Martin's, the art school famous for its fashion graduates Alexander McQueen and Stella McCartney, then went to New York to do a fine arts degree at Parsons School of Design.

Then, still a couple of years short of his inheritance, he became a model - his impish, finely-chiselled face suited the waif period perfectly. He appeared in a Paul Smith advert and modelled Alexander McQueen's "bumster" trousers. "I didn't enjoy modelling very much," he says. "But I was a student, living in New York and I didn't have much money and I could earn a lot in one hour - so of course, I did it."

He met Stella in New York and she still lives there half the time. When she's in London, they're now more likely to be found at home, says Macmillan, where he cooks endless amounts of pasta.

"She thinks I'm a really good cook," he says proudly. "The Italians have got it right. Food is very sensuous."

And big bowls of pasta give a girl some healthy curves, I point out. "Ooh, yes," he says. "Phwooooaarr."

So cosy, couply nights in - can Macmillan really have become so boring? Not if his new range of clothes, launched at a trade show in Berlin earlier this week, is anything to go by.

I wonder how the swastikas (some of the T-shirts have swastikas in the American flag with the words "Kill! Kill! Kill!" printed on them) went down in Germany. "They weren't offended because they knew it was about America," he says. "This is Michael Moore on a T-shirt."

He might not get off so lightly with the Islamic militants - a print on the inside of his jackets features Osama bin Laden's head stuck on bodies engaged in sexual acts with men and women. Saddam Hussein and Carlos the Jackal are engaged elsewhere in Macmillan's orgy, while giant phalluses grow around the writhing bodies like mushrooms.

"It's a take on the Marquis de Sade, we call it 'Weapons of Arse Destruction'. We don't take ourselves too seriously. It's all very tongue-in-cheek. We don't try to shock or be sensationalist." I find that hard to believe. "I have extreme ideas which can get people's backs up but it's not intentional."

The rest of the collection features T-shirts with prints taken from all the things Macmillan and co-creator Giles Curties are currently into, including Sixties B-movies, old books, hip hop and punk culture, Cuban revolutionaries, Arabic script, Masonic symbolism, weapons and the Iraq war.

Some are genuinely arresting, others predictably puerile (a T-shirt from the women's range reads "vagnificent"). But the schoolboy jokes are the only cheap thing about the collection - the T-shirts cost from £40, the pornographically-lined jackets from a whopping £300.

The range should soon be available in Selfridges. Macmillan's own shop, Zoltar the Magnificent, closed earlier this year. "It had run its course. I wanted to get back to being creative rather than being stuck behind a till." Is it true that he turned people away for being too ugly? "Not me, certainly not while I was there," he says, though he won't say if it was someone else at the shop.

Zoltar the Magnificent sold Macmillan's early fashion collections but it was the interior of the shop that got people talking: more swastikas, machine-guns covered in McDonald's logos, the walls of the loo were papered with pictures of women performing oral sex on men and there was a room known as the "Gimp Chamber", painted black and kitted out with dominatrix fittings.

Real orgies (as opposed to artistic ones) or not, is Macmillan obsessed with sex? He is typically evasive and fiddles with his hair again. "It's only human. It's the reason we're here, isn't it?"

He smiles so sweetly and appears so innocent that it seems impossible to believe those lurid, debauched tales. Almost.