Witnesses describe the alleged attack on Leona Lewis at the book signing
Police have arrested a man over an alleged assault on 2006 X Factor winner Leona Lewis at a book signing.
A Scotland Yard spokesman said police were called to Waterstone's book store at Piccadilly, London, but Lewis did not need hospital treatment.
Lewis's spokesman said the singer had been signing autographs for around 90 minutes when "a guy came up and punched her to the side of the head".
The spokesman added that Lewis was "understandably badly shaken".
In a statement, Waterstone's said: "There was an incident at our Leona Lewis signing this afternoon and the event was immediately stopped.
The security all jumped on him and they were trying to pull him out and he was just laughing
"We are now doing everything we can to support the police in their inquiries."
Lewis had been signing copies of her new autobiography, Dreams, which is due to be released next month.
One fan at the scene told the BBC: "My brother saw the whole incident. He [the attacker] walked up there with the book, she signed it and, as she looked up, he just punched her.
"He [my brother] actually heard the impact."
Another eyewitness added: "She was running out with her hand over her eye and I just saw a man on the floor.
"Suddenly the security all jumped on him and they were trying to pull him out and he was just laughing, he thought it was funny."
Lewis's spokesman added: "The police were called immediately and medical attention has been sought.
"Leona's understandably badly shaken and apologises to the fans she was unable to meet and complete signings for."
Waterstone's said it took security at book signings "extremely seriously" and this was the first incident of its kind it had encountered.
"We would like to thank Leona for her professionalism and we are extremely sad that this event was ruined for her, and her fans, many of whom queued from the early hours of the morning to meet her," it added.
Lewis had been scheduled to appear on the BBC's The One Show on Wednesday night; however a spokesperson confirmed she had pulled out.
BBC sports presenter Gabby Logan was brought in to replace her.
Lewis's second album, Echo, is scheduled for release in November.
The three-time Grammy Award nominee released her debut single A Moment Like This shortly after winning the ITV1 show.
She is due to play a gig in her native Hackney in east London on 2 November.
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