The game is on! Work on 'Sherlock' season 4 has begun, say showrunners

Filming for season four of the BBC's Sherlock has begun! And we have the news from the horse's mouth itself. Or the horse's Twitter account. Or something.[caption id="attachment_2715938" align="alignleft" width="380"] Benedict Cumberbatch and Martin Freeman in Sherlock[/caption]Anyway, to get back to business, the official Twitter account of Sherlock had a rather cheery message for fans on Wednesday evening. "It begins... Filming for series 4 is underway!" the tweet read. It was accompanied by a rather un-cryptic clue in the form of the hashtag #221Back with the show's co-creator and onscreen Mycroft Holmes — Mark Gatiss — tagged on the tweet.A very short video of Mark Gatiss holding up a clapboard for Sherlock, and saying, "We're back. The game is on!" was also released. The director's name — Rachel Talalay — can also be seen on the clapboard.In January this year, the team had released a special one-shot episode of Sherlock, called The Abominable Bride. While fans had waited for a long time to see the Sherlock-Watson pair, played by Benedict Cumberbatch and Martin Freeman, respectively, on screen again for a long time, Abominable Bride prompted mixed reactions.Fans' impatience for the fourth season of the show is understandable considering that the third season had aired all the way back in the first quarter of 2014.However, with both Cumberbatch and Freeman pursuing their extremely successful Hollywood careers, as well as making time for other acting commitments (such as in theatre), getting the stars to commit to a shooting schedule for Sherlock has been difficult.It is expected that season four will see the return of Sherlock's arch nemesis — Moriarty.