The UK-based World Conker Championships is investigating allegations of cheating after the men's champion was found to have a steel chestnut in his pocket, an official said on Tuesday.
The tournament, which takes place in Northamptonshire in central England every year, sees competitors use conkers -- the seeds of horse chestnut trees -- threaded onto string to try to smash their opponent's nut.
Eighty-two-year-old David Jakins, nicknamed "King Conker", won the men's event on Sunday at his 46th attempt after competing in it since 1977.
But he has been accused of using a metal replica by his defeated finalist Alastair Johnson-Ferguson, who told the Telegraph newspaper that he suspected "foul play".
It was shaped and painted brown to look like a real conker, the paper reported.
"My conker disintegrated in one hit and that just doesn't happen," 23-year-old Johnson-Ferguson said.
St John Burkett, of the competition's organising committee, told AFP that it was "still investigating" the claims but suspected that Jakins had not cheated.
"Various evidence has come to light, which means we still need to gather further testimony. A video has emerged, which we are looking at closely," he said.
Jakins denied using the metal replica in the tournament and said he only carried it around with him "for humour value", according to the Telegraph.
"The evidence looks as if it may exonerate Mr Jakins but we need to confirm through further corroboration," Burkett told AFP.
More than 200 people took part in the tournament, which raises money for charity and was attended by about 2,000 spectators.
Competitors often wear elaborate headwear. This year, one man wore a green inflatable Yoda headpiece, while another wore a conker-themed hat.
Jakins lost to the women's champion in the overall final.