Screenwriter Niall Leonard - who is married to the best-selling author - had an uncredited role in the Sam Taylor-Johnson-directed first film, and has been drafted in to pen the much-anticipated sequel, titled 'Fifty Shades Darker'.

Producer Michael De Luca told The Hollywood Reporter: ''Niall is an outstanding writer in his own right, with multiple established credits, and we are lucky to have him join Team Fifty.''

The first film in the 'Fifty Shades' series was widely panned by critics and it has since been announced that director Sam Taylor-Johnson will not be returning for the next movie.

Sam was asked to return for the sequel, but decided to walk away amid reports she struggled to work alongside E.L James.

Earlier this week, Sam told BANG Showbiz: ''I'm flattered they wanted me to continue. But it was a monumental job - that was enough for me.''

The director also said she was surprised by the reaction to the film's release and passed on her best wishes to the next director.

She explained: ''I couldn't really have ever expected that after working in a small, dark room for almost a year editing.

''I wish them all the luck in the world.''