Rachel McAdams has confessed she was a bit nervous at the prospect of starring in the new Sherlock Holmes movie.

“I always get nervous before I start – at the beginning even,” the actress, who plays Sherlock’s love interest Irene Adler in the Guy Ritchie film, tells Access Hollywood.

“Fortunately, I think Irene isn’t as well known to the general public so we have a little bit of room to experiment with her which leaves the door wide open.”

Rachel will star opposite Robert Downey Jr who plays Holmes and Jude Law as Dr Watson.

“Irene is mentioned in the book as ‘the woman‘ and the only woman Sherlock has ever mentioned,” says Rachel.

The entire cast emphasized the fact that this will be a sexier, more action-packed Holmes, but also made reference to the fact that his bare-knuckle boxing and martial arts skills are deeply rooted in the writing of Sir Arthur Conan Doyle.

For her part, McAdams describes her character as an underworld adventuress with a criminal mind, but who also has her romantic and “delicious” sides. She says it will be a pleasure working with Downey Jr. and Ritchie, whom she calls a “collaborative, experimental director.”

While the character only appeared in that one story, McAdams’ personage would return for any possible sequel.

Warner Bros. Pictures has set a November 20, 2009 release date for the Guy Ritchie-directed Sherlock Holmes movie.