WASHINGTON -- Sue Vertue, the producer of the BBC’s detective series "Sherlock," wasn’t sure of how to use Twitter three years ago when the show premiered.
"We joined Twitter about a week before it was going out -- the air date was sooner than we expected," she says. "We thought ‘God, how can we make sure that everyone knows that it’s going to go out?’ "
Now, "I seem to spend my life on Twitter telling people when it’s not going out."
The latest season of "Sherlock," a contemporary version of Sir Arthur Conan Doyle’s classic detective Sherlock Holmes, is airing Sunday nights (check listings) on PBS’ "Masterpiece Mystery!" "Masterpiece" was a co-producer.
The stars, Benedict Cumberbatch (Holmes) and Martin Freeman (Watson), now are world-famous for other roles such as Khan in "Star Trek: Into Darkness" (Cumberbatch) and Bilbo Baggins in "The Hobbit" (Freeman).
Vertue wondered, when the actors arrived back in the U.K. to shoot season three, if their fame would make a
"I have to say I was slightly nervous," she said. "It’s been quite a while and since then the boys have gone off and done such huge things. I was just a little bit worried that, well, they’re going to have these two massive Hollywood stars turning up in the middle of Wales."
There was no problem. "It was easy. Everyone just slotted in exactly to what we knew. It’s a bit of a family thing now, you know, same crew have been working now on the series, a lot of the same people, so it’s like coming home almost."
Each of the 90-minute shows takes roughly 24 to 25 days of filming. Vertue, who is married to show runner and writer Steven Moffat, says "There’s a lot of pages that you do in a day in these TV shows." They try and do "as much (filming) as they can in camera," not using special effects.
Except, she says, "Obviously, we didn’t blow up the Houses of Parliament" in episode one, "The Empty Hearse."
In the second episode, "The Sign of Three," John Watson’s wedding "cost us a lot to film it. It was like we were at a week-long wedding, everyone in their finery. We just thought, by the end, that we were at this lovely wedding."
She says that most of "Sherlock" is filmed in Wales with "a bit in London," specifically the exterior shots outside 221B (Baker Street), Holmes’ apartment.
The popularity of the show has led to avid fans gathering for the outdoor shots. "The boys (Cumberbatch and Freeman) said it’s like doing sort of live television because you’re doing a small scene outside a door and there’s, on the other side of the road, about a thousand people standing there."
She says the fans are "incredibly well-behaved."
"They’ll move around" when the show needs them to, she says. The crew says, " ‘Right, we need all of you up that end of the road, we’re shooting that way,’ and they all just move up and down the road really."
"They are very well-mannered," she adds. "Long may it continue."
"Sherlock" fans span the globe. "They seem to fly in. A lot of them sort of know each other now. They’ve met behind the barriers, sort of; people from different countries turn up and meet their friends that they met from the last series. It’s quite sweet."
Sherlock Holmes himself has changed from the previous season. After faking his death in "The Reichenbach Fall" and returning to life Holmes finds he’s now faced with social situations he’s never experienced, such as being best man at Watson’s wedding to Mary Morstan (Amanda Abbington).
"We wanted to come back and humanize him a bit," says Vertue. "I suppose (we wanted to) lull people into a slight sense of security, and then by the third one, obviously, that’s much darker story."
She says future episodes for the rumored seasons four and five are still being planned. Moffat and writer Mark Gatiss (who also plays Mycroft Holmes) "had quite a lot of meetings and they thought everything out. Eventually, when they are secure in their heads where they’re going, then they pull me in and they pitch it which is quite nice."