Martin Freeman has said the success of the BBC1 drama Sherlock was "a lovely surprise".
The actor, who played Dr Watson in the updated version of the classic detective stories, starts filming the second series next year.
He said: "I always thought it was good and I always think we believed in it but the extent of its success was a lovely surprise."
He went on: "I don't think any of us banked on it being so across the board successful."
The series, which updated Arthur Conan Doyle's stories to 21st century London, was a ratings hit, pulling in more than seven million viewers.
Martin will film the new episodes with co-star Benedict Cumberbatch, who plays Holmes, in between stints in New Zealand where he is filming Peter Jackson's two-part Lord of the Rings prequel The Hobbit.
He said: "January I go out and I'm out there until May then I come back and do Sherlock and then I go back until December and make the second part of the Hobbit."