The star of Sherlock talks guns, The Office and meeting new Doctor Who Matt Smith…

What do you like most about playing Watson?
“I like playing people who are not particularly happy, and Watson isn’t very happy until he meets Sherlock. He helps Watson find a purpose again, which is akin to his old life of adventure in the Army and he gets his mojo back. It’s great he’s not just the sidekick, too. There is no question that Sherlock is the focus, but Watson is pretty parallel.”

Did you avoid other versions of Sherlock Holmes?
“Actually, before we started filming we all went to see the Guy Ritchie version and really enjoyed it. Sherlock Holmes is so famous it outstrips any one telling of it. No version is the definitive one; it’s about everyone having their go.”

Were the action scenes fun?
“I didn’t do any real stunts, but I did enjoy the fact Watson is handy with a gun. He’s not bumbling and academic or too English and repressed.”

Did you learn how to fire a gun?
“I’d done it before, but not often. I’m sure people like Jason Statham are more au fait with it. I don’t really like guns. I’ve always got in my mind an episode of Columbo and the idea that someone has tampered with the weapon. I asked the armourer about 50 times, ‘Is this loaded?’”

Does it bother you when people talk to you about The Office?
“It happens to me daily and for the first couple of years I thought, ‘Enough already’. I understand it now because I loved the show myself, but it’s nice being in other countries where people have no idea who I am. It reminds of what life used to be like.”

Have you ever met John Krasinski who plays Tim’s counterpart in the American version of The Office?
“No, but I’d love to. He looks like me apart from being three feet taller. It was surreal watching him at first, but then you just get into enjoying the show, which is testament to how well they do it.”

Sherlock is co-written by Stephen Moffat. Would you like to be in Doctor Who?
“I don’t feel as passionate about Doctor Who as Stephen does, but I’ve enjoyed watching it more since being a father. We met Matt Smith while filming Sherlock in Cardiff because the Baker Street set is next to the TARDIS set. It was strange seeing Sherlock Holmes and the Doctor together. They are the perfect fictional team.”

Would you like to work more in America?
“Absolutely, but it has never been my main ambition. I wouldn’t want to move there, though. I’m very English.”

*Sherlock screens on BBC One on Sunday evenings