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Police have arrested a man over an alleged assault on former X Factor winner Leona Lewis at a book signing.

A Scotland Yard spokesman confirmed police were called to Waterstone's book store at Piccadilly in London but said Leona Lewis "did not require hospital treatment".

Lewis, who won the X Factor in 2006, was signing copies of her new autobiography, Dreams.

Bystanders waiting to have their books signed described what they thought had happened in the store.