Sherlock fans teased with ominous series 4 trailer starring Benedict Cumberbatch

Benedict Cumberbatch fanatics may be overlooking the prospect of Christmas and wanting to fast-forward to New Year's Day when the man in question graces the small screen as Sherlock once again.

The first episode of the new series will air on 1 January 2017 with Cumberbatch and Martin Freeman, and the BBC has just released a cryptic advert ahead of the launch, just to tease viewers a little bit more.

The short clip that aired on Wednesday night (30 November) saw Freeman's Watson and Sherlock sitting in their 221b Baker Street home in what appeared to be a flooded set.

The two men, who appeared either nonchalant or dismissive of the waters rising around them, continued to sit in silence as if nothing was wrong. A teasing caption then appeared on screen with the words: "It's not a game anymore."

Sherlock's fourth series will commence on New Year's Day with the first of three brand new episodes. Details about the forthcoming series have been successfully kept under wraps by show bosses – but the first episode is called The Six Thatchers. This suggests that it could be based on Sir Arthur Conan Doyle's The Adventure of the Six Napoleons.

Further hinting at this, the BBC released a statement claiming: "Sherlock waits to see where Moriarty will make his posthumous move. One mysterious case in particular baffles Scotland Yard – but Sherlock is more interested in a seemingly trivial detail.

"Why is someone destroying images of the late Prime Minister Margaret Thatcher? Is there a madman on the loose? Or is there a much darker purpose at work? Something with its roots deep in Mary Watson's past..." it continued.

The grim teaser most certainly supports co-writer's Steven Moffat's promise of "an emotional upheaval" for the characters on the hit drama this series.

He previously claimed: "[Series four] is going to be [about] consequences. It's dark in some ways – obviously it's great fun and a Sherlock Holmes romp and all that – but there's a sense of things coming back to bite you."

The last series ended with a hint that Andrew Scott's character, Moriarty may be back, despite being previously thought of as dead.

On the highly-anticipated series, Cumberbatch claimed that it will be "the last one – for now", but that he'd "never say never" to reprising his role as Holmes in the future.

He also said: "We're all doing other things now and you'll have to see the fourth season to realise why, for now, it's not going to happen again at the same regularity that it has been happening."

Sherlock returns to BBC One with The Six Thatchers on 1 January.