British singer Leona Lewis was attacked as she signed copies of her autobiography in central London on Wednesday, police and the book store said.
Lewis, who won the British TV talent show "The X Factor" and has topped charts around the world since, was signing copies of her book "Dreams" at a Waterstone's book store in Piccadilly Circus when she was assaulted.
"We can confirm that there was an incident at the Leona Lewis signing this afternoon," a Waterstone's spokesman said.
"The event was immediately stopped by the security guards present and the police are talking to the individual concerned."
Police said officers had arrested a 29-year-old man on suspicion of assault occasioning actual bodily harm. The man is now being questioned at a central London police station.
"My brother saw the whole incident," one fan at the book store told the BBC. "He (the attacker) walked up there with the book, she signed it and, as she looked up, he just punched her."
Lewis, whose debut album entered the US charts at number one in 2008 -- the first British woman to achieve the feat, was badly shaken by the incident but did not need hospital treatment, her spokesman said.