Shopping in London is the ultimate pleasure, admits Benjamin. He finds it inspirational, educational and thrillingly old-school. "I love old things," he says. "In the US, we are not that old. We have old stores and cool vintage stuff, but nothing like you have over here."
Benjamin is an oddity in the sartorially prescriptive rap fraternity. A renaissance-man alternative to the aggressive knuckleheadery of, say, 50 Cent, Benjamin paints, reads, acts and plays the violin (and many other instruments). A vegetarian, he campaigns for Peta, the anti-fur lobby. Musically speaking, the 32-year-old from Atlanta, Georgia, who is one half of OutKast, is at the cutting edge of gonzo hip-hop with hits such as Ms Jackson, Roses and Hey Ya!, but when it comes to his wardrobe, he's 80% Brideshead.

He likes the rake of our straw hats and the equestrian cut of our traditional suits. He favours shirts with cutaway collars, rugby jerseys, brightly coloured hoop socks and co-respondent shoes. He likes the temperate British climate because it means he can wear one of his many Scottish tweeds. Talk to him and he'll reference the Duke of Windsor and Beau Brummell. When it comes to dressing, "those guys killed it," he'll tell you.

Benjamin's frequent trips to London find him trawling Portobello market for vintage tweed, cords and old shoes. On Jermyn Street, he'll check out the shirts and ties at Turnbull & Asser, Hilditch & Key, New & Lingwood, then make a short diversion to St James's to see the hats at Lock ("If you ask me, a good hat can make or break an outfit") and Lobb's exquisite bespoke shoes a few doors along. Then it's Henry Poole on Savile Row, where he'll finger some gold-braided Napoleonic livery, leaf through one of the old order books, maybe order a blazer.
Hackett, the young Sloane's outfitters, is his favourite stop-off. Benjamin spends a small fortune there and knows all the staff. "You might think that a rapper from the deep south of America might not be our typical customer," admits Hackett's co-founder Jeremy Hackett. "But the fact that Andre comes at our clothes from a different perspective, not burdened with any of the preconceptions about class and sartorial stereotypes that a British customer might have, means he looks at the clothes in a new and fresh way. He puts our stuff together in a way that we never imagined and he is totally fearless with colour combinations. He's got a really good eye."

Benjamin has got the fashion thing bad. It's been like this ever since he was at Sutton middle school in Atlanta. Back then, there were two rival gangs stalking the corridors and hanging out by the lockers – the prep crew and the soul kids. "The soul kids wore Jordache jeans cut at the bottom, Stan Smith sneakers, silk shirts and Starter jackets," he says. "The preppy kids were from better homes and they could afford the preppy clothes. Tretorn tennis shoes, madras pants, Ralph Lauren polo shirts, mostly. They had the coolest girls and they had Volkswagen Rabbit [Golf] cars."

Sometimes the two gangs would clash in elegantly wardrobed street violence. "You know, like in the 1950s when you had gang fights? Like West Side Story? It was like that. You had a whole other side with guys that were from the streets but dressed like they were rich preppies."
Most notorious was a preppy gang called the Stray Cats, who wore Benetton tennis bags slung over their shoulders. "Only thing was, nobody played tennis. But they used to take the racquets to school and use them as weapons whenever they got in a fight."

Benjamin, an only child, wanted to be a preppy but he was never in a gang. "My mom was too strict to ever let me get involved in that stuff." After his estate agent mum and collections agent father split up, his mother worked on the production line at General Motors to make ends meet; money was tight. "If I wanted nice clothes I'd have to wait for Christmas. I couldn't wait. I got a job. But if you couldn't buy them, you stole the clothes. Or you'd get your girlfriend to steal them for you."

Increasingly frustrated by his hometown's lazy, parochial attitude to fashion, Benjamin and a school friend would buy dye to colour their jeans. "We were trying to find ways to be individual, find our identities, I guess." They would pore over men's fashion magazines and watch old movies. Benjamin became fascinated by the understated Anglophilia and Gatsbyish exotica of Ralph Lauren adverts, which peddled dress codes that appeared to have been handed down from father to son like family heirlooms. "I think a lot of African-American kids don't have fathers to teach them how to dress, so you end up being taught by pictures in magazine and movies. You see cowboys, Indians, old Hollywood films, Cary Grant. It has an effect on you."

Was there something subversive about a poor young black kid dressing up in the preppy duds that were the privileged mufti of the Wasps? "A little. I guess it's all about the twist, really. Everything is slower in the south. But we wanted to educate ourselves. Every kid was a fashion victim back then, but as you get older you learn and you become the killer not the victim."

But before Benjamin could mutate into a gentleman designer, he embarked on a sartorial journey that took him beyond button-down collars and deck shoes. "When I decided to become an entertainer things became even more extreme," he says. OutKast – Benjamin and another high school friend, Antwan "Big Boi" Patton – released their first album, Southernplayalisticadillacmusik, in 1994. But despite the influence of Cameo and George Clinton in the music, they looked fairly conventional. Hip-hop seemed to tame fashion-forward Benjamin for a while. "If you watch the career of OutKast, look at all our pictures and videos, you'll see that at the start, even though I was writing out-of-this-world lyrics, I really just wanted to fit in, wearing baseball jerseys and sneakers. But the more I got into what I was doing, the more I started to think, to hell with what everyone else is doing.

"When the OutKast sound changed and I started producing my own records, I would mirror what I thought that character doing that music would look like. As the sound got a little wilder, freakier and funkier, so did the clothes. Then when the sound got more sophisticated, the clothes changed again."

At first, he channelled the outlandish get-ups of his funk and rock heroes – Cameo, Funkadelic, Sly Stone, Hendrix even. He wore white wigs and designed himself a pair of fake-fur pants. He scoured fabric shops in Atlanta for material – "upholstery fabric, mainly" – commissioning a reliable and creative network of seamstresses in the area. Then the outfits got crazier. Once, on the Chris Rock TV show, Benjamin decided to debut an outfit that included American football shoulder pads customised with multiple feather boas and ski-boots. The only problem was he had forgotten the trousers. "Big Boi dared me to go out and perform on stage in just my underwear. So I did. And it was the most fun."

But beneath the boas and ski boots, hip-hop's peacockish, dapper rapper was nurturing commercial fashion ambitions. "And I knew that fur pants and white wigs are not sellable." The market is now thick with rap and urban musicians who have tried their hand at (or lent their names to) designing clothing – Justin Timberlake's William Rast, Gwen Stefani's LAMB, Pharrell Williams's Billionaire Boys Club – but Benjamin is determined that Benjamin Bixby (the "Bixby" was added for its pleasing alliterative qualities) should develop into a label that might compete with fashion's major players.

When he showed his collection in a hotel suite last year, Vogue editor Anna Wintour came to have a look. "'I can see longevity in this business,' she told me, 'but you have to get with people in business who understand that this is not just an overnight entertainer brand, that you want this business to grow.'" Benjamin took her advice. He chose not to use the apparently readymade brand name of Andre 3000 (one of several alter egos he has). "Andre 3000 would be cool if I wanted to do a low-end brand and sell it in Wal-Mart, but this is not a celebrity brand. I am not a fan of celebrity brands, to be honest."

As well as sketching designs for tweed plus-fours, bomber jackets and waistcoats, he now makes factory visits, has the help of collectors and fashion archivists, and employs a technical director and a vice-president of design. "I would like to go to fashion school to learn the correct terminology and the correct technique," he says.

Benjamin seems thrilled at how well the label has been received. The major menswear magazines have featured the line, admiring its quality, detailing and tailoring. And, much to his delight, the other day that perennial rock'n'roll dandy Mick Jagger was spotted taking a picture of the clothes in a window at Barney's New York. "That," says Benjamin, finger-snapping the air with unbridled satisfaction, "felt pretty good".

Story by. Simon Mills