Andre Roussimoff makes for an unlikely icon. The French wrestler was the star of America's World Wrestling Federation during the 1970s, and continued to fight until 1991, under the name of Andre the Giant. He also appeared in the 1987 film, The Princess Bride and played a Sasquatch in a couple of episodes of The Six Million Dollar Man. Such showbiz accolades are fine, but they alone hardly place him alongside Chairman Mao, Che Guevara and Marilyn Monroe, as one of the most widely recognisable faces in popular art. Yet black and white renderings of Roussimoff's face grace thousands of sites around the globe, often accompanied by the word "Obey".

The wrestler's latterday fame can be put down to one man: street art supremo, graphic artist, advert lampooner and occasional ad industry employee, Frank Shepard Fairey, whose new London exhibition opened this week.

Shepard, as he's been known since childhood ("it's a family name, people have said 'oh Shepard! You are shepherding the masses! Do you have a messiah complex?"'), cut his first sticker stencil of the wrestler in 1989, during the summer break after his freshman year at The Rhode Island School Of Design.

This image and the accompanying "Andre The Giant has a posse" slogan began as an in-joke among local skaters. Interest grew, and Fairey used Andre stickers and posters to undermine a couple of prominent ad campaigns. Then, in 1995, he updated the design, emboldening the face and adding an Obey slogan, which he took from the anti-advertising B-movie, They Live.

What sets Fairey apart from other graffiti fanatics is the scale of his Giant campaign. The Andre image predates most other street-poster graffiti artists and Giant heads have been plastered up in Japan, Russia, Italy and Paris, as well as numerous sites throughout the UK and the US. Even British stencil artist, Banksy, cites Fairey as an influence.

"I think he really liked how prolific I was," says Shepard, seated in the Brick Lane warehouse which will serve as his gallery. "When he travelled almost anywhere, he'd see my stuff, and he knew that it was mostly me putting it up."

He puts some of his determination down to an unfortunate source.

"I'm diabetic," Fairey says. "I'm probably going to die 15 to 20 years before most other people. So, it's just the meaning of life thing: what does it all mean?"

The wiry 37-year-old then laughs a little, before adding: "it means nothing!"

"I've had a vitrectomy in both eyes," he continues. "That's when they cut your eyeball open and they take out all the gel and fill it with saline solution."

Surgical complications can include cataracts and retinal detachment.

"I've been temporarily blind in both eyes, but not simultaneously," he says, "one occasion was about a year ago, and the other happened about four months ago."

In the second instance, he was in New York to open a show.

"It makes me feel," he says, smiling and staring forward, "as if I'd better get busy."

To fund graffiti projects, Fairey founded first a screen-printing business, then a clothing company and a graphic design agency, taking work from everyone from Pepsi and Sunkist to Levi's and the Smashing Pumpkins.

"Of course people say - and I'm quoting the Bill Grundy Sex Pistols interview now - 'isn't that slightly opposed to your anti-materialistic view of life?'"

He smiles. It's a question he gets a lot, so he knows his answer already: "I'm not against capitalism. If I was, I wouldn't live in the US. If you get up everyday, work and spend money, you're participating. But that doesn't mean I don't want to critique it."

His attitude towards advertising is a little more ambiguous. In the past, he's said he feels like a double agent. Indeed, in 1994, Fairey set out to sabotage the ad campaign for a new drink from Coca-Cola called OK, which was aimed at hard-to-reach, anti-establishment, grungy young males. Now Fairey is the go-to man when appealing to that demographic.

"Coca-Cola were trying to steal the cachet of a subculture in a really soulless way," he remembers. "I don't have a problem with someone making something good and saying it's good. Like the iPod: it holds 10,000 songs, it's useful, it's got a lot of memory. Alright, cool, I'll take one."

He remains a conduit for reaching disaffected, affluent kids. Why? Perhaps because, unlike some graffiti artists, he comes from a comfortable background.

"I grew up in South Carolina, in a conservative, small city," he explains. "My mom had been head cheerleader and my dad was captain of the football team. She taught English and he was a doctor."

Fairey was privately schooled and he used his mother's photocopier - bought for Mrs Shepard's domestic room rental business - to print up his pre-Andre skate stickers.

"She would say 'don't put that sticker paper in the machine, it jams it up!'" he remembers.

Certainly, where his art is concerned, Fairey is still appealing to alienated kids.

"When I was a teenager, all art was album covers, graphic art and skateboard T-shirts. I want to influence people at a stage in life when they're not too jaded to say 'It's just all bullshit anyway. Fuck it.' I'm trying to get them to see that building blocks are all very basic, like three chords in rock'n'roll. It's easy to follow."

Though the red, white and black Obey posters are simple enough, works from this London exhibition are a little more complex. There are fewer Giant heads, while dollar bill designs, Islamic patterns and female portraits join the wrestler's face. The show's title, Nineteeneightyfouria, is a reference to London. Shepard believes the British capital to be not only the world's foremost street art city, but also the one metropolis where the blanket CCTV coverage deserves the adjective 'Orwellian'.

"The surveillance is insane," he says. "There's this loving embrace of shrinking privacy and civil liberties."

Despite this, street art flourishes. Within days of arrival, Shepard has pasted up large works around the gallery's adjoining streets and can cite art by similar graffiti practitioners within a quarter mile radius of his Brick Lane space. He believes London's vitality can be put down to his friend Banksy.

"Most street art makes that primary impression," Shepard explains, "but Banksy is the first guy to realise how he can leverage secondary impressions through the media. There are a lot of guys who have been doing street art. They were known within their subculture, but only after the splash that Banksy has made have they been able to sell at art shows."

While buyers of Fairey's work might count an Obey Giant print as a great piece of leftwing wall jewellery, Shepard's own politics remain nuanced. He has turned down commissions from Marxist organisations, and believes that a little bit of competition is a good thing.

"I think that when people don't see the ability to get ahead for themselves, they're demotivated," he says.

For Fairey, the competition not only includes cops and corporations, but also rivals. A number of graffiti artists have devoted themselves to defacing Obey Giant sites. The most recent is a New Yorker who goes by the tag of Splasher. In the past few years, Splasher has defaced a number of Obey Gaint pieces in NYC; yet even he seems to have fallen foul of Shepard's work ethic.

"We put 40 new pieces up there in June," says Shepard, "and only about one had been splashed. I think Splasher has retired. People ask 'is Splasher going to make you stop?' and I'm like 'well, I've been doing this for 20 years. I'm going to outlast the guy.'" He smiles again, before adding: "I'll outlast all of them."

· Nineteeneightyfouria is on now until November 25, at StolenSpace, The Old Truman Brewery, Brick Lane, E1, see stolenspace.com for info

Urban renewal

Other street artists to look out for in the area

Space invader

Small tiled renderings of space invader game characters on Brick Lane, London, E1

"We showed him at our gallery in Los Angeles and I've showed at his gallery in Paris. His work stays up for a long time because people don't think of it as graffiti."

Banksy

Stencils above the corner of City Road and Old Street, London, EC1

"This image is no longer there. I actually did that spot once Banksy had been gone over; he said it was cool. Later somebody wanted to defend Banksy's honour and wrote something on there, but I had no idea it was going to stir up some controversy."

D-Face

Car sculpture in the yard at the end of Dray Walk (off Brick Lane), London, E1

"I love his work; he and I went out postering togther. This sculpture across the street, the car with the big ball, I like."