We revealed Banksy's name 15 years ago - so why was the arty set still insisting last week that it's a mystery? Is it because it would be harder for a privately educated chap called Robin Gunningham to flog his graffiti for millions?

He's the poster boy for the country's chattering classes and art world - a man feted for creating works that poke fun at the Establishment, while, famously, hiding his identity. Under the pseudonym Banksy, he has become a global star with an estimated £50 million fortune. His Girl With Balloon has been rated the 'nation's best-loved work of art', more popular than John Constable's The Hay Wain. The results came from a poll, based on a list compiled by arts writers including the Observer's media correspondent. But there is an egregious hypocrisy behind all this hero-worship. Banksy's reputation and financial pulling power rely on the mystique of his anonymity. And although his real name has been public knowledge for 15 years, thanks to a Mail on Sunday investigation, Banksy's fawning fans connive to ignore this fact. Instead of calling him by his real name - Robin Gunningham - there is a surreal omerta, with his true identity deliberately camouflaged. This, according to art experts, allows him to exploit his carefully-nurtured image as 'the Scarlet Pimpernel of modern art' and make even more money as someone who wears his street-cred like a hairshirt.