The beautiful actress told Cosmopolitan that she'd read for the central role of Anastasia Steele, the naïve university graduate who falls for the mysterious billionaire Christian Grey, a man with a passion for racy sex.
"That audition was so uncomfortable," admitted Lucy.
"It's exactly what you thought it would be: a big monologue but very, very sexual ... there were some things that I was so embarrassed to be reading out loud, but it's one of those things where you have to commit wholeheartedly or you're going to make a fool of yourself."
The role eventually went to actress Dakota Johnson, while Christian is being played by gorgeous Northern Irish actor Jamie Dornan.
Fifty Shades Of Grey is based on the first book in E.L. James' erotic trilogy of the same name.
Fans went crazy last month when the first full-length trailer for Fifty Shades was revealed, giving us a glimpse at how Ana and Christian's passionate relationship would play out on screen.
The movie hits cinemas on Valentine's Day next year.
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Watch the trailer in full here: