It's just under a month until Christmas Day and as a result we've been sent a sniff of the eagerly awaited Doctor Who Christmas Day special to really whet our appetites until December 25th's big reveal. We already know that the episode, mysteriously titled 'The Time of the Doctor,' will see Matt Smith's Doctor pass on the baton to Peter Capaldi's for the new season but we hear the show's writers have some pretty big surprises in store.

Doctor Who Christmas Poster
Cybermen & Snow: The Doctor Who Christmas Special Is Set To Be A Stonker.

The newly released teaser from the BBC is only 10 seconds long meaning the plot of the Christmas Day episode is still very much cloaked in mystery but the trailer gives a doomy vibe along with the message "Silence Will Fall."

The episode will tackle the highly disputed issue of regeneration. It was initially thought that Smith was the 11th Doctor but John Hurt's Doctor is rumoured to be the ninth, making Smith the 12th. This set fans abuzz will speculation regarding the Doctor's purported 12 regeneration limit.

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DW writer Steven Moffat attempted to clear things up for fans at the Doctor Who Official 50th Celebration at London's ExCeL: "[Smith] has no more ever called himself the 11th Doctor than he would call himself Matt Smith. The Doctor doesn't know off the top of his head [what number he is]," he said, via Metro.

"If you worry about such things, and I do, then I specifically said John Hurt's Doctor doesn't use the title. [Matt Smith's Doctor] is in his 12th body but he's the 11th Doctor, however there is no such character as the 11th Doctor - he's just the Doctor - that's what he calls himself," Moffat added cryptically.

Watch The Doctor Who 'The Time Of The Doctor' Teaser:

He also addressed the notion that Paul McGann's Doctor might be the same as John Hurt's. "Paul McGann turns into John Hurt so they're not the same incarnation," said Moffat. "He used up another regeneration and I'll expect he'll be in trouble shortly - you can't break rules laid down in The Deadly Assassin. [A Tom Baker story]" Huh? Well we're pretty confused but apparently that's all we're getting for now.

Irish actress Orla Brady will reportedly star in the Christmas episode as "someone from the Doctor's past." This is similarly shady news too: it looks like we'll just have to wait until Christmas Day.