David Howell, from Seaford, East Sussex, astonished the game's authorities yesterday when he beat John Nunn, one of the world's top hundred players, at the Mind Sports Olympiad at Olympia, London.
David, the under-nine and under-ten British chess champion, said: "I'm quite excited by the win. I thought I was going to lose quite badly." The previous youngest player to beat a grandmaster was 10-year-old Murugan Thiruchelvan.
"It does leave one a little bit speechless," said Sidonie Henbest, a spokeswoman for the tournament. "David is well on the way to becoming a grandmaster himself."
David first played the game at the age of five, when his father, Martin, 48, bought an old chess set at a jumble sale. Dr Howell said last night that he had never intended his son to get into the game. "I am not a chess player. I only played on Sunday afternoons at university. I taught him to play and he made sense of the game very quickly, in about an afternoon."