Sam Taylor-Johnson and Jamie Dornan visited prostitutes to research 'Fifty Shades of Grey'.

She said: "Jamie and I met various dominants and dominatrix, just to make sure we understood that world, so that we in no way portrayed it incorrectly."

Part of Sam's research involved a thorough understanding of E.L. James' novel and she admits she has read the raunchy tome so often, she feels like she has "eaten" it.

She told Red magazine: "I've practically eaten it. I have read it over and over."

The 47-year-old filmmaker - who has daughters Angelica, 17, and Jessie, nine, with ex-husband Jay Jopling and Wylda, four, and Romy, two, with husband Aaron Taylor-Johnson - admitted her dedication to the project has left her going "out of her mind" because she has been so consumed with the movie.

She said: "I'm literally going out of my mind. I have seen this film over a thousand times and I'm now in a blancmange. But the nuances within - the tiniest shift, look, blink of an eye - can make all the difference and flip it into the wrong territory

"The moment I stepped out of the meeting [after accepting the movie], I stepped onto one of those bullet trains. The doors closed and I couldn't get off. The speed, the velocity, was unbelievable. I need to get off and breathe and think about something else."