Downey, Jr upsets Sherlock expert with name slip

Robert Downey, Jr upset the world's foremost Sherlock Holmes expert by calling the super sleuth's sidekick by his first name in his new movie.

The actor befriended Malibu, California-based tax lawyer Leslie Klinger while preparing to play Holmes in Guy Ritchie's sequel Game of Shadows but they fell out when the know-all saw the film for the first time.

Downey, Jr says, "I guess I dropped the ball. He was very upset... I said, 'Les, what happened?' He said, 'You called him John!' I was like, 'John Watson, that's his name...'

"He goes, 'He would never call him John. Only call him Watson or Mr. Watson...' It didn't feel right when I said it; I should have trusted my instinct."

And the actor insists he has taken Klinger's comments about his portrayal very seriously: "Thank God there are experts. People take (Arthur Conan) Doyle's interpretations of these characters so seriously. They're fantastic books."