The time is nigh: current Doctor Who timelord Matt Smith will prepare to meet his maker in Christmas Day's eagerly-anticipated special episode of the BBC sci-fi drama. On December 25th we'll see Smith hand over the sonic screwdriver to new Doctor Peter Capaldi but the technicalities of the change-over are driving Whovians crazy.

Doctor Who Poster
It May Be Christmas On Earth But There Are Still Monsters To Battle For The Doctor.

There's still the question of whether Smith in in fact the 12th, and possibly final Doctor. 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.

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

The newly-released trailer for the Christmas episode, titled 'The Time of the Doctor,' doesn't shed a whole lot of light on the ins and outs of Smith's transition to Capaldi but does give an enticing glimpse into what is sure to be a stonker of an episode.

How on Earth did Daleks get into Buckingham Palace?!

Although we see a lot of the usual fake snow, we are given a look at Orla Brady's character Tasha Lem with her striking eye make-up and red and black beehive. We hear her announce "The siege of Trenzalore has now begun," referring to the planet the Doctor knows will bear his grave.

Doctor Who Time Of The Doctor
'The Time Of The Doctor' Ties In Festive Celebrations With A Sorrowful Departure.

We see a dalek zipping about through flames from an explosion saying "The Doctor is regenerating" whilst Smith roars "If you want my life, come and get it!" Jenna-louise Coleman's Clara seems frantic, urging that the future be changed and reciting, "Now it's time for one last bow, like all your other selves.

She continues: "The eleventh hour is over now, the clock is striking twelve," perhaps referring to the regeneration limit.

Doctor Who Alien
The Silents Will Also Feature In The Christmas Day Special.

The dark and tense episode leaves a lot of questions unanswered about the pivotal episode, which will be aired in a fortnight's time. Smith hasn't been more much helpful either, though has promised that fans won't be let down. "I'm really excited about Christmas. I think Steven [Moffat] has written a real belter for me to go out on and I had a great time filming it," he said, via The Mirror.

"It was quite sad at the end, obviously, when I had to leave, but I think we've got a really moving story, a really great sense of adventure in it. "It still feels like a classic adventure episode with great monsters and a few twists," the actor added.

Doctor Who's 'The Time Of The Doctor' will air at 7.30pm on BBC One on Christmas Day.