Casting rumours are generally best ignored (how many of those Spider-Man casting whispers have come true?), but this one comes from a generally reliable source, so there's surely something to it. Entertainment Weekly is reporting that Robert Downey Jr is in the frame for Sherlock Holmes, which Guy Ritchie is set to direct. This will be based on Lionel Wigram's forthcoming comic book, rather than Arthur Conan Doyle's books directly, so expect more sword-fighting and boxing, and less deerstalker-wearing and violin-playing.
Is casting an American as Holmes sacrilege? Generally speaking, it might be, but this is Robert Downey Jr. As long as he can nail the accent (and we vaguely remember him doing a good job in Chaplin and Restoration) then there's nothing to say he wouldn't be fantastic in the role. He's got experience with substance abuse to draw on. He's proved he can do action in Iron Man. He can do wit and intelligence.
This is still just something he's apparently eyeing – along with a number of other projects including Brett Ratner's Hugh Hefner biopic – and no contracts are said to have been signed. Also there's the small question of the Iron Man sequel, which could see him tied up for a good part of next year, when Holmes would probably also shoot. But could you see him as the great detective?