Blek le Rat is known to many as the godfather of street art and to the French as its grandfather. But having honed his craft for more than 30 years, the spry 61-year-old, whose real name is Xavier Prou, has no intention of retiring. Despite being France's graffiti art pioneer (he says he was the second to make street art in Paris, after Zloty Kamien), he is most famous for being the artist whose style the pseudonymous Banksy "stole". Blek's spray-painted stencils of rats first appeared on the banks of Seine when Banksy, who is thought to be nearly 40, was still at primary school. In his unauthorised biography Banksy said: "Every time I think I've painted something slightly original, I find out that Blek le Rat has done it as well, only 20 years earlier."
For a while, Blek and Banksy were mutually appreciative of each other. But the graffiti world revels in minor spats between its giants and Banksy is not one to keep matey with his rivals for long. During an interview with Blek at his rather wonderful family home, an hour's drive east of Paris, he showed me emails from Banksy that accuse Blek of mocking him and in which the tone is less than friendly. "The last email he sent me said, "Blek, are you making fun of me? Stop saying that I take my ideas from you'." Blek, dubbed by the British press as "Banquesy", is frustrated by the email exchange and says he cannot reconcile how he feels about the rivalry.
That his signature style has been taken and made more recognisable, not to mention profitable, by another artist, is "very emotional", he says. In the past, he has publicly expressed his anger, both on Channel 4's Graffiti Wars documentary and in interviews. But these days, he is more resigned to the comparison and remarks, rather sadly, that whatever he says about Banksy it will be taken out of context and that he will be accused of jealousy.
"It's difficult because on the one hand I'm very happy: without Banksy I would not have the position I occupy in the street art movement. I'm recognised in the US, UK, Australia and around the world. It helps me make a living. It's great! But on the other hand, I [have] seen how he manipulates the art market. I can see that we probably needed someone who could do this for street art, like Damien Hirst did for conceptual art, so it's very interesting. But it does make me uncomfortable."
I'm in Blek's charming rural French house to discuss an exhibition charting his 30-year career curated by Jean-David Malat, which opens at the Opera Gallery in London on Friday. Blek is sitting at a long table in the dining room of the glamorously ramshackle property that was bought by his grandfather in the 1920s and is stuffed full of worn antique furniture. Traditional portraits on the walls contrast with a mad assortment of boldly colourful canvases and stencilled panels from the artist's own atelier, propped up against the walls or stuck on doors. It is très très chic.
The graffiti movement is often associated with artists from working-class backgrounds who are unlikely to have studied at art school but instead perfected their craft while avoiding arrest for vandalism. Blek, who grew up in the rather swanky 16th arrondissement of Paris and studied at the prestigious Ecole Nationale Supérieure des Beaux-Arts (first fine art, then architecture), is clearly not of this ilk. But that's not to say that introducing street art to Paris, or making a name for himself, has been easy,
"The first time I saw graffiti art was in New York. I was 21 and had been invited by an American friend who studied with me at university. I worked for three months to save the airfare and when I got there I was absolutely amazed. It was July 1971 so it was hippie time. The streets were full of art, music, and political protest against the Vietnam war." He found the contrast to France extraordinary. "You can't imagine what Paris was like then. It was 25 years after the war but it was like the 19th century. There was nothing for young people, no music, no art."
During his American adventure, the 20-year-old Blek was utterly confused by the tags he noticed in the New York Subway. "I asked my friend, 'Why are people doing this?' Writing their names? I couldn't understand what tag signs meant, or why people painted crowns of faces on them? Nobody understood, nobody knew. The images were very strong. I had seen political slogans painted on walls in Paris, of course, but this had no obvious purpose."
Returning to Paris with the kernel of an idea, Blek asked his art school friends if they'd be interested in trying out some graffiti. They weren't interested. It would take another decade for this first burst of inspiration to find form.
He spent the years between his lengthy architectural studies and his emergence as one of the most exciting graffiti artists working as a teacher. At Adventureland, a progressive after-school club where he worked in 1980, Blek watched children steal paint and brushes from a local supermarket and use them to decorate the walls of an old warehouse. "I suddenly knew I had to make graffiti because the kids were already doing it. Kids of seven years old gave me the idea."
His first attempt didn't go very well. "The first time I tried, in 1981, I tried to imitate American-style graffiti, but I found the technique very difficult. The result was absolutely terrible." He knew that rather than replicate the more expert daubings he'd seen in New York, he'd have to find some other way of doing it. He drew on his art school etching and printmaking training, as well as a more unorthodox inspiration.
"When I was a kid I made a trip with my parents to Padua, Italy, and I saw graffiti there made by the Fascists. Propaganda stencilled on walls. I remember asking my father about them. The faces of Mussolini stencilled in the street stayed with me." It was this combination of influences, the American and the Fascisti, that led him to develop his stencil-style.
He started with rat stencils to emphasise his new name, which was a play on well-known 1960s comic character Blek le Roc ("rat is also an anagram of art"), but also because there was something ratty about an artist who scuttles around under the cover of darkness. "Paris is full of rats, but you never see them. I wanted to say to Parisians, 'Your city is very beautiful, but don't forget that your basements are full of vermin'. I have heard that there are more rats than people living in the city.
He is glad of the position he holds as a pioneering street artist. But he is ashamed of the money-grabbing nature of modern artists. "The art world is a big mess," he says. "Nobody cares who is a real artist. It is all about cheating people out of money."
Blek predicts a major revolution in the art world in the next 20 years. "The street art movement started 40 years ago in the US, but we are still only at the beginning. Artists will find new ways to display and sell their work that will have nothing to do with galleries and investors." Until then? "I'll keep working. But only on public walls. I'm too old for illegal ones."
Blek le Rat, Opera Gallery, London W1 (020 7491 2999; operagallery.com) 27 April to 18 May