'Doctor Who' has been missing from the telly schedules for a year. But it's back this Christmas for a festive special. It stars Peter Capaldi as The Doctor, as well as Charity Wakefield, Justin Chatwin and Matt Lucas. It's set in New York City... and it's a superhero story.
'It was in a script we had for a different episode,' showrunner Steven Moffat told us. 'I suggested it in one of my flights of fancy, because you must always be able to say anything in scriptmaking – however mad! Nobody liked that idea at all and I was told to shut up.'
But a few months later the idea came up again in a conversation about the Christmas episode. 'I got my one and only opportunity to write a superhero story. I think it's a lovely episode,' he says.
He'll be watching the Christmas special as it airs. 'There's something extraordinary that you learn in that moment. The awareness that the nation is watching clarifies things. You suddenly think, “Hang on, that's not clear at all” or “That's much funnier than I thought it was”. It's quite a bracing experience'.
But he won't have much time to reflect. He's currently penning episodes for 'Doctor Who' series 10, which will introduce Pearl Mackie's new companion Bill – 'I'm in the absolute war zone of "Doctor Who". I've got mountains to climb.' And he's also thinking about his 'Who' legacy, because, after six years at the helm, Moffat is handing the Tardis keys to 'Broadchurch' writer Chris Chibnal next year.
'I hardly ever think about the fact that it's the end. I will shortly, I imagine. When it comes to it I'm sure it'll be tremendously sad.'
'For quite a long time I thought last series was going to be my last one,' he says, admitting that he wrote his idea for a final send-off last Christmas. 'Having laughed at my great big ending because Chris wasn't available yet I carried on for another year.'
'I do have an idea of what I'd like to do for my very last episode. It's not some ghastly self tribute or anything – it doesn't matter to the audience at all that I'm leaving – but there's something that would please me to do at the end and I think it could please the audience too.'
But he's got a while to go yet. 'A year from now I'll be talking to you about the next "Doctor Who" Christmas special,' he laughs.
'Doctor Who' is on Christmas Day at 5.45pm on BBC1. Watch the trailer here.
More TV? Here's our pick of the best TV to watch this Christmas.
Fancy a film? Here are the best movies on TV this Christmas, the best Christmassy movies on TV and the best Christmas movies of all time. Plus, the best movies on Netflix and the best family-friendly kids' movies on Netflix.