From the East End of London to Bethlehem and Hollywood, Banksy's sardonic graffiti has made him as world famous as an anonymous artist possibly can be.

Last night the future of the notoriously secretive spray painter and the multimillion-pound industry he has created were in doubt after a newspaper claimed to have unmasked him. Banksy, it suggested, is the pseudonym of Robin Gunningham, 34, a former public schoolboy from Bristol.

The artist's representatives refused to confirm or deny the report, which was based on interviews with dozens of friends, former colleagues, flatmates, enemies and family members over the course of a year.

Five years have passed since a landmark show in Shoreditch started Banksy's rise from street artist to maverick darling of celebrities such as Angelina Jolie. Art world insiders predicted yesterday that the world's most famous graffiti artist may now simply melt away.

Banksy's identity has always been a closely guarded secret, known only to a small circle of friends and associates. He has done only one full newspaper interview and never publicly attends his exhibitions. Although his canvases sell for hundreds of thousands of pounds each in the finest auction houses, his roots and passion remain in illegal street art, for which a protective cloak of anonymity is useful, if not essential.

The most plausible clue to Banksy's identity was a photograph taken in Jamaica four years ago showing a man in blue shirt and jeans with a spray can at his feet. The Mail on Sunday took the photograph to Bristol, where a former neighbour of Mr Gunningham identified him as the man in the photograph.

A classmate at at Bristol Cathedral School remembered Mr Gunningham as being “extremely talented at art” and a decent rugby player. “I am not at all surprised if he is Banksy.”

Mr Gunningham left the school at 16 and is believed to have drifted into Bristol's thriving graffiti subculture. He moved to Hackney in 2000, sharing a flat with a man who worked for a record label for which Banksy drew album covers.

However, neither of Mr Gunningham's parents recognised the man in the photograph. Mr Gunningham himself has apparently disappeared.