LONDON (AFP) ― The film version of erotic best-seller “Fifty Shades of Grey” will star British actor Charlie Hunnam as Christian Grey and Dakota Johnson as Anastasia Steele, the book’s author E L James said on Monday.

The casting of the movie, to be directed by British filmmaker and artist Sam Taylor-Johnson of “Nowhere Boy” fame, has been one of the most hotly anticipated secrets in Hollywood.

But instead of big names, the producers have gone for up-and-coming stars.

Hunnam starred in this summer’s sci-fi blockbuster “Pacific Rim” while U.S. actress and model Johnson is the daughter of veteran “Miami Vice” star Don Johnson and Oscar-nominated actress Melanie Griffith.

“I am delighted to let you know that the lovely Dakota Johnson has agreed to be our Anastasia in the film adaptation of Fifty Shades of Grey,” author James said on Twitter.

About an hour later she announced: “The gorgeous and talented Charlie Hunnam will be Christian Grey in the film adaptation of Fifty Shades of Grey.”

She also confirmed the casting in statements on her website.

Johnson, 23, had her screen debut with her mother in the 1999 film “Crazy in Alabama.” More recently she starred in the David Fincher movie “The Social Network” and the U.S. television sitcom “Ben and Kate.”

Hunnam cut his teeth in the British children’s drama “Byker Grove” and appeared in the 2006 dystopian thriller “Children of Men” before his appearance in giant-lizards-versus-robots blockbuster “Pacific Rim.”

Spiced up with sado-masochism, the 2011 novel “Fifty Shades of Grey” was the first part of a trilogy about a relationship between a college graduate, Anastasia Steele, and a young business magnate, Christian Grey.