Doctor Who: Twice Upon A Time. Christmas Special 2017.

It's been an exciting few weeks for all fans of the world's most celebrated Time Lord, with the announcement of a new Doctor - and a woman at that!

But, first, before we can do that, we have to get rid of the old one.

In fact, so mammoth a deal is the introduction of the first female Doctor that it looks like we're going to have to get rid of two old ones simultaneously, with both Peter Capaldi and William Hartnell/David Bradley forced to meet their maker.

It all sounds epoch-making in the extreme but just what can the trailer tell us about it and will the great woman herself be putting in an appearance?

No. It turns out she won't.

But, then, I don't think anyone with any sense ever thought she would. In fact, not a lot puts in an appearance in the trailer. We get no real clue as to the plot, the villain, the tone or the jeopardy. In fact, all we really find out is that four familiar faces are in it and that an instant has been frozen in time.

That, of course, brings back memories of Hell Bent and Clara being snatched from death, thanks to the moment just before her doom being frozen by the Time Lords, causing her to exist in an instant between her heartbeats. From this - and the fact that all previous multi-Doctor tales have featured the Gallifreyans - I conclude that those pesky timesters are behind all this episode's drama and that that'll give Clara the chance to return for Capaldi's goodbye.

One return I could have done without is Mark Gatiss. I'm sure he's a lovely bloke but it's starting to feel like he's surgically welded to the show. He's written an episode in nearly every season since the show came back in 2005, and played at least three different characters in it. I wouldn't mind if his episodes had been classics and he had the acting prowess of Ian McKellen but the truth is his writing and his acting have been no more than serviceable at best. If there's one thing Chris Chibnall, as new showrunner, could do to win me over, it's finally freeing us from the power of Gatiss.

Anyway, my big prediction is that this whole episode takes place in a Time Lord snow globe. I don't have a clue what a Time Lord snow globe is but this is a Steven Moffat story, so there's bound to be some sort of gimmicky tricksiness going on and, this being a Christmas special, and me associating snow globes with Christmas, this is the tricksiness I'm anticipating.