Martin Freeman and Amanda Abbington
Martin Freeman and Amanda Abbington Reuters

"Sherlock" has managed to retain its appeal primarily because of its "intermittent" nature, believes Martin Freeman, who essays the role of John Watson in the detective drama.

There is usually a gap of two years between seasons, and the fourth season will air only in 2016. But show executives have planned a Christmas special by the end of 2015, and the cast is currently filming the one-off episode.

And this break in between seasons is what makes the show fresh and gives the actors time to take up other projects, said Freeman during an interview with the Independent.

"It's so intermittent. That's what for me makes it doable," said Freeman, adding: "I don't know about [Benedict Cumberbatch], but certainly for me it would soon lose a lot of its appeal if we were schlepping that around for eight months of the year, every year. A bit of the sheen would have gone off it."

Over the years, "Sherlock" has become such a huge global phenomenon, catapulting the lead actors to instant stardom. Interestingly, this has resulted in fans, mainly women, hanging out at filming locations, making it difficult for the actors to do their jobs.

"When we're [filming at] our stand-in for Baker Street, it is hard to do your job. And I don't love it," Freeman told The Independent. "It's like trying to act at a premiere. … I wasn't in The Beatles. But I've never seen anything like it. There's such a heightened sense of excitement, so every time we come out, there's applauding — and it's like, 'No, can you n—.' Or, if we do anything — 'Cut!' — applause. … It's like, 'No, this isn't a gig.' "

Although filming is underway, it is not immediately known which original work of Sir Arthur Conan Doyle is being adapted. But speculations are rife that it could be "The Adventure Of The Blue Carbuncle," a part of which was already introduced last season.

Last week, director Douglas Mackinnon further sparked speculation when he tweeted a photo of an on-camera image with a quote from "The Adventure of the Blue Carbuncle" that read: "The stars were shining coldly in a cloudless sky."

Co-creator Mark Gatiss tweeted the same picture with yet another quote that read: "It was a bitter night, so we drew on our ulsters and wrapped cravats about our throats..."c/o ace @drmuig! #Sherlock."