The X Factor winner was attacked by a crazed fan while signing copies of her autobiography at a London store in 2009.
Today's in-store appearance marks her first signing since the incident. Eight extra bodyguards will be at HMV's Oxford Street branch to protect the singer.
"Leona will never get over what happened in 2009," a source told The Sun.
"This signing is a big deal as it will bring back horrible memories, and she wants to ensure it doesn't happen again."
Lewis, who releases her third studio album Glassheart today, recently revealed that she recorded 'We Found Love' before Rihanna.
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