British actor Jude Law has signed on to play Dr. John Watson in the upcoming movie Sherlock Holmes, director Guy Ritchie said at a London news conference.

Robert Downey Jr. is to play the titular sleuth in the film, which also is to co-star Rachel McAdams, Mark Strong and Kelly Reilly and which is to open in theaters next October.

Law is best known for his roles in The Talented Mr. Ripley, Alfie and Cold Mountain.

Ritchie's credits include Lock, Stock and Two Smoking Barrels, Snatch and the current release RocknRolla.

The BBC said Ritchie and producer Joel Silver said their new adventure movie based on the mysteries of Arthur Conan Doyle will be shot in London for three months at locations such as St. Paul's Cathedral and Freemasons' Hall.

I'd like to bring something new to this project -- I have a few tricks up my sleeve. It won't be a traditional Guy Ritchie thing, it will be a new Guy Ritchie thing, the BBC quoted Ritchie as saying.

I think me and Guy are well-suited to working together, Downey said. The more I look into the books, the more fantastic it becomes. Holmes is such a weirdo. (c) UPI