[Shaun]

Britain's Charlie Hunnam and US actress Dakota Johnson have landed the coveted lead roles in the big-screen version of erotic bestseller Fifty Shades of Grey.

Author EL James revealed the news on Twitter, ending months of speculation over who would play Christian Grey and Anastasia Steele.

Hunnam, 33, is best known for his work in such TV shows as Queer as Folk and US biker drama Sons of Anarchy.

Johnson, 23, is the daughter of Miami Vice star Don, and Melanie Griffith.

She appeared with Justin Timberlake in 2010 release The Social Network and played the female lead in US TV show Ben and Kate.

Artist and film-maker Sam Taylor-Johnson will direct the movie version of James' novel, scheduled for release in August 2014.

Published in 2011, Fifty Shades of Grey follows the sexually-charged relationship between billionaire Christian and college student Anastasia.

The novel and its two sequels, Fifty Shades Darker and Fifty Shades Freed, have become a literary phenomenon that earned James, 50, a reported $95m (£61.5m) last year.

The author called Hunnam "gorgeous and talented" and Johnson "lovely" as she revealed their joint casting to the world.

The former is no stranger to the big screen, having played a lead role earlier this year in summer blockbuster Pacific Rim.

To many, Johnson will be a less familiar proposition, though some may recall her appearances in such comedies as 21 Jump Street and The Five-Year Engagement.

I smell a flop~