Robert Downey Jr. adds punch to the role of Sherlock Holmes in an action-packed movie that breaks with what its makers called stuffy screen interpretations of the fictional English detective.

The Warner Bros. production, which opens on Christmas Day in the United States, is widely expected to become a major new franchise for the studio just as the lucrative Harry Potter series comes to a close in 2011.

I think it potentially has franchise capabilities which I think is very good, producer Joel Silver told a news conference ahead of the picture's world premiere in London on Monday.

I think we have a chance of really having a lot of fun with this ... story. I think that you want to have a place to go with a movie ... and I think we tried very hard to allow the audience to embrace that there may be more of a story.

Downey Jr.'s Holmes is a physical, fist fighting, streetwise version of the super sleuth in an attempt by director Guy Ritchie to ditch common associations of pipe smoking, deerstalker hats and the famous phrase elementary my dear Watson.

Ritchie, famous for his 1998 heist movie Lock, Stock and Two Smoking Barrels and an eight-year marriage to pop star Madonna, also sought to place Holmes and Dr. Watson, played by Jude Law, on more equal footing than previous adaptations.

The deerstalker and 'elementary my dear Watson' never happened, actually, and the deerstalker is never referred to in the books, Ritchie said.

Although we all are aware of the obvious symbols of Sherlock Holmes, (we) made a decision early on that if we were going to do this we'd have to dust off Sherlock Holmes and create what we thought to be an authentic Conan Doyle version.

STUFFY CHARACTERS

Silver described earlier adaptations of the Arthur Conan Doyle novels and short stories, featuring actors like Basil Rathbone and Jeremy Brett, as stuffy.

But in reinventing the character and his relationship with Watson, Law said Ritchie had been true to the original stories.

I knew from them (Downey Jr. and Ritchie) that it was going to be a different take on the older films of Sherlock Holmes and it fascinated me.

Obviously they were coming to me not to put on two stone and fall around and put my foot into waste paper baskets, he added, referring to Watson's big-screen image as a bumbling foil to the brilliant Holmes.

They were going to come and ask me to play Watson with a bit more edge. What was intriguing ... was to go back to the books and realize how much of this new rediscovery, if you like, was also in the source material.

The storyline of the latest Holmes film centers around a new character Lord Blackwood, an unrepentant killer sentenced to death but who apparently returns from the grave to haunt 1890s London and hatch a plot that could destroy the country.

Although everything else is cherry-picked from the short stories and the novels, Blackwood isn't, and I think what that allowed the film to do was create whatever we wanted, said British actor Mark Strong, who plays the villain.

Professor Moriarty, Holmes's nemesis in the original Conan Doyle tales, is expected to appear in subsequent installments should the franchise materialize.