Magnus Carlsen leaves Sinquefield Cup amid Niemann chess ‘cheating’ furore

The chess world is in turmoil after the world champion, Magnus Carlsen, pulled out of a major tournament for the first time in his career with frenzied speculation over whether an opponent cheated.

On Monday, organisers of the $500,000 (£433,000) Sinquefield Cup announced additional anti-cheating precautions, including a 15-minute delay in the broadcast of the moves and increased radio-frequency identification checks. But Carlsen had already withdrawn from the event, announcing it in a tweet with a video of José Mourinho saying: “If I speak I am in big trouble. Big, big trouble.”

Carlsen did not offer any further explanation but the American grandmaster and popular streamer Hikaru Nakamura said Carlsen had pulled out because he suspected his third-round opponent, Hans Niemann, was “probably cheating”.

The 19-year-old Niemann, who has made spectacular progress into the world’s top 50, shocked Carlsen on Sunday by beating him with the black pieces. Niemann said that “by some ridiculous miracle” he had guessed what his opponent’s obscure opening would be and prepared deeply for it that morning. “Magnus must be embarrassed to lose to me,” he said.

But while many praised Niemann’s victory, others were more sceptical. They included Nakamura, the world’s highest-rated blitz player, who said Carlsen would not quit an event without good reason. “Magnus would never do this in a million years,” he said. “He just doesn’t do that. He’s the ultimate competitor, he’s a world champion.

“He wouldn’t do this unless he really strongly believes Hans is cheating with a very strong conviction. I think he just thinks Hans is just cheating, straight out.”

Nakamura, who is closely affiliated with the world’s biggest chess website, chess.com,