Jude Law is to play Doctor Watson in Guy Ritchie's upcoming Sherlock Holmes film, it has been confirmed.
Robert Downey Jr, whose new film Tropic Thunder is out now, has already been confirmed for the lead role for the detective drama.
And speaking at a London press conference, Ritchie confirmed that Law will star as the detective's sidekick.
Snatch director Ritchie was contracted by Warner Bros Studios in June to helm a film based on an as-yet-unpublished graphic novel take on Sir Arthur Conan Doyle's most famous creation.
"I'd like to bring something new to this project - I have a few tricks up my sleeve," he said on Wednesday. "It won't be a traditional Guy Ritchie thing, it will be a new Guy Ritchie thing."
Filming begins later this month in London, with locations set to include St Paul's Cathedral and Freemasons' Hall.
Mean Girls actress Rachel McAdams is set to play Irene Adler, a love interest of the enigmatic Holmes while Mark Strong, who played mob enforcer Archie in Ritchie's most recent film RocknRolla, is attached as the villainous Blackwood.
British starlet Kelly Reilly, last seen in horror film Eden Lake is to Mary, Doctor Watson's love interest, it was confirmed today.
Downey Jr was announced as Holmes in July and Law's attachment to the project emerged late last month.
"I think me and Guy are well-suited to working together," said Oscar-nominee Downey Jr.
"The more I look into the books, the more fantastic it becomes. Holmes is such a weirdo."
Sherlock Holmes - the film's working title - is due for release in October 2009.