Benedict Cumberbatch shooting for top secret BBC project

Fans are agog with excitement, anticipation and frustration, with one user commenting beneath the Facebook post: “That’s all?! You can’t leave me with this!!!!”

Benedict Cumberbatch. Tim P Whitby / Getty Images

“Benedict Cumberbatch filming something special for BBC One and BBC Two. More details soon ...”

The teaser, which was put up on the BBC One’s Facebook page a few days ago, was accompanied by images of the British actor.

Ben Stephenson, the BBC’s controller of drama commissioning, said: “He was great. Stay tuned,” in response to the announcement.

Cumberbatch shot to fame with his portrayal of the famous detective in the popular BBC series Sherlock, adapted from Arthur Conan Doyle's Sherlock Holmes stories. The third season was broadcast earlier this year.

But what is the BBC referring to and why is it top secret?

It can't possibly be the fourth season of Sherlock because it was announced months ago: in July, the BBC said a full-length, special episode of Sherlock will begin filming in January 2015, and the series (each season features three 90-minute episodes), will be filmed later in the year.

There is speculation that Cumberbatch might be working on a short, 45-minute episode that will be broadcast before the mini-series and special episode hit screens around Christmas 2015 (a date has not been ­announced yet).

Then again, the FB post might be linked with a fund-raising project for the BBC's official charity Children in Need, but some believe the images either are scenes from Doctor Who or his forthcoming BBC Two film The Hollow Crown, in which he portrays Richard III. But www.radiotimes.com reported BBC sources as claiming that it is definitely not Doctor Who. It also said that whatever it is Cumberbatch is working on, will be broadcast on both ­channels.

Meanwhile, fans are agog with excitement and frustration, with one user commenting beneath the Facebook post: “That’s all?! You can’t leave me with this!!!!”

Another said: "Ohh BBC, you tease. It doesn't look like ­Sherlock, 'cause of the hair. But if it's worth a tease, it must be something good."

Cumberbatch won an Emmy this year for Outstanding Lead Actor in a Miniseries for his role in Sherlock: His Last Vow, the final episode of season three, which gathered seven awards in total.