FIFTY Shades of Grey hits cinemas this Friday - just in time for Valentine's Day and already looks set to be a box office hit.

With 500,000 advance tickets sold in the UK, Sam Taylor-Wood's eagerly anticipated screen version of E.L. James' novel is poised for a whip-cracking opening weekend.

James self-published the first instalment of her raunchy trilogy before the first hardback edition was released in March 2012.

Critics might have been less than flattering, giving the book a sharp verbal spanking, but the public were seduced by James' depiction of the intensely physical relationship between a college graduate and a handsome businessman and propelled the tome to the top of the bestseller lists on both sides of the Atlantic.

In the UK, such was the clamour for copies of the paperback that Fifty Shades Of Grey outsold JK Rowling and Dan Brown, author of The Da Vinci Code, and opened the floodgates on a raft of books crudely dubbed 'mummy porn'.

The story sees literature student Anastasia Steele (Dakota Johnson) interview and then fall for charming multimillionaire businessman Christian Grey (Jamie Dornan).

In order to get closer to the object of her affections, the student submits to Christian and he introduces her to an erotically charged world of domination.