The trailer for the Doctor Who Christmas special has been released, showing the regeneration of eleventh doctor Matt Smith.

The BBC has released the 30 second trailer for the Christmas special, entitled "The Time of The Doctor", due to air on Boxing Day on Prime TV in New Zealand Christmas Day.

The episode will be Matt Smith's last outing as the Time Lord before twelfth doctor Peter Capaldi takes his place.

The trailer opens ominously with narration from Jenna Coleman as Clara Oswald, before a mysterious woman says the "siege of Trenzalore is now begun", where Smith's Doctor is set to regenerate into a new body.

As a house explodes into flames, a Dalek can be heard saying: "The Doctor is regenerating."

Jenna Louise Coleman told TimeOut last month about appearing alongside her co-star Matt Smith for the last time.

Smith's last scenes, she says, were an emotional experience.

"The entire episode was. I knew it was going to be very hard to see him go. It doesn't feel real at the moment. I think it took us both by surprise how emotional the episode was and is. It feels like the Doctor and Clara have just got into this place enjoying their adventures together, and it's almost that it's been cut too short in a way and it's kind of what makes it beautiful as well."

Doctor Who writer Steven Moffat also said recently he thought Peter Capaldi's incarnation of the doctor was "worlds away" from his Thick of It character Malcolm Tucker.

Speaking to SFX magazine, he said: ""I'm confident that we'll sell this Doctor to our existing audience and he will be different enough that people won't just be miserable that they're missing Matt."

Prime is screening all of season seven of Doctor Who in its daytime schedule on Christmas and Boxing Day before the Christmas Special at 8.30pm on Boxing Day.