"IT'LL blow your socks off" Stourbridge educated writer SJ Watson - author of Before I Go To Sleep - has told fans wondering how the forthcoming movie based on his best-selling novel will turn out.

The film, based on Watson's critically-acclaimed psychological thriller and starring Oscar-winning stars Nicole Kidman and Colin Firth, is currently being filmed in London and Surrey.

SJ Watson, real name Steve Watson, told fans on his Facebook page on Friday: "Lots of you asking when the film's out. “It's likely to be early 2014. Also, lots wondering whether it'll do justice to the book (thank you!) - I've read the script and seen some of the early footage and, trust me, it'll blow your socks off."

Steve's comments coincided with the release of the first official picture of stars Nicole Kidman and Colin Firth filming together.

Moulin Rouge actress Kidman takes on the role of amnesia patient Christine who wakes every day to remember nothing of the day before.

While British star Firth (The King’s Speech) plays her husband Ben - in the film which is being directed by Bafta-winner Rowan Joffe and produced by Ridley Scott’s production company Scott Free.

British actor Mark Strong (Tinker Tailor Soldier Spy) also stars, as psychotherapist Dr Nash, in the movie which takes a sinister turn as terrifying truths emerge that force Christine to question everyone around her.

Steve, aged 42, who grew up in Wordsley - attending The Wordsley School when it was known as Buckpool and Stourbridge’s King Edward VI College, has spoken of his amazement at having his book turned into a major movie and he described seeing the likes of Kidman and Firth bringing to life the characters he invented as “surreal”.

Although he previously admitted he “used to sort of fantasise that it would be a film one day and that Hollywood actresses would be interested” as he penned the book in his spare time while working at St Thomas's Hospital in London as an NHS audiology specialist.

Since its release in April 2011, Before I Go To Sleep has been published in more than 42 countries and has become one of the most successful debuts ever.

The movie, which is already being tipped by film fans as a must-see, is expected to hit cinema screens in 2014.