ET was in London to speak to the stars of the highly anticipated blockbuster 'Sherlock Holmes,' starring Robert Downey Jr. and Rachel McAdams. 

The Guy Ritchie-directed film, due to begin shooting this month, will feature Downey Jr. as famed detective Sherlock Holmes in a mystery that promises a fresh take on the classic Sir Arthur Conan Doyle character.

The movie will present Holmes as more adventurous and less formal than previous screen incarnations and Downey Jr. says he is excited to take on the new action-packed challenge, saying it promises to be "big and fun."

He also reveals he'll have a lot of intense fight scenes in the film, which he says should be no problem for him since he has been training in martial arts for the past five years.  

The 43-year-old actor's new project comes on the heels of his hugely successful blockbuster 'Iron Man,' which has already earned $318.3 million for Paramount Pictures at the U.S. box office.  

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."  

Based on a forthcoming comic book written by the film's producer Lionel Wigram, 'Sherlock Holmes' will be distributed by Warner Bros for release in 2010.