Serendipity struck, then, in the creation of the War Doctor who represented the original run and thus eased the worry of how to involve past Doctors. We also got a new sense of momentum for the show: not the Doctor’s quest for Gallifrey, so much as a new set of ideas to explore over the next three series. We have the Doctor as an ideal, a code that he tries to live up to but can break, and Hurt’s reaction against the 10th and 11th Doctors would be replicated by Peter Capaldi. Elements of this story would be used to develop the Doctor’s backstory, building towards his relationship with Missy in Series 10 – what’s really strongly developed here is the death toll the destruction of Gallifrey would involve and how this would be one of the foundations moving forward. This is a show for children and so there’s a development of the idea of children on Gallifrey with the number of them lingering in the Doctor’s mind before and after he uses the Moment (an inspired use of Billie Piper), which in turn leads to the child in the barn in ‘Listen’ and the backstory suggested by ‘Hell Bent’ and the Doctor’s conversation with Bill about the Master in ‘World Enough and Time’. Yes, going forward we would have Capaldi’s more wintery Doctor, but also we’d have a show where the Doctor’s childhood loomed larger than ever before.
3. A Christmas Carol (Christmas Special, 2010)
Written by Steven Moffat. Directed by Toby Haynes.

It’s the best Christmas special isn’t it? Romantic and melancholy and resonant with its “halfway out of the dark” motif. It manages to include flying sharks into a riff on Dickens’ A Christmas Carol – with your actual Michael Gambon as Scrooge – without it seeming a bit much. While Moffat’s cleverness is ostentatious and this can wind people up the wrong way, let’s look at something he said on the ‘City of Death’ DVD extras: “Douglas Adams brought to Doctor Who something completely useless. He brought the revelation of what Doctor Who would look like if it was written by a genius. Well, there just aren’t too many geniuses, so I don’t know that there’s much to learn from the way he did it.”
The thing is, Moffat and Russell T. Davies also demonstrated what Doctor Who would look like if written by a genius: a fricking flying shark in a Dickens adaptation. Doctor Who can do that, almost no other show can, and so frankly Doctor Who should be colliding ideas together like this as often as it can. Moffat has spoken of the show using up ideas at a tremendous rate, and certainly he seems to fritter away concepts that could power a story on a grace note or background detail, or set up one idea only to veer away from it when another one takes over. Yes, every single character he writes is hornier than a teenage unicorn, and yes, you can spend every single episode he writes waiting tensely for sex comedy that would have got written out of the second draft of a Carry On film, but nonetheless we have been spoiled by this double whammy of geniuses running the show, and if there is anything to learn it is that.
2. Flatline (Series 8, Episode 9, 2014)
Written by Jamie Mathieson. Directed by Douglas Mackinnon.

While ‘Mummy on the Orient Express’ felt like a high concept episode realised extremely well, ‘Flatline’ is a whole other level of creativity. In terms of writing the show like you own it, Mathieson is at an even higher gear here by combining strong characterisation with an eye for the medium: visuals that few other shows could manage that range from the horrifying (the human nervous system on the wall, the juddering march of the boneless creatures) to the joyous (the Doctor’s hand scuttling out of the tiny TARDIS doors like Thing from The Addams Family). Mathieson detailed parts of the creative process on his website, where he describes the meetings that ensued after he was told the story needed to be Doctor-light after he’d already done two drafts. There’s a sense here, though, that Mathieson spent three weeks rewriting ‘Flatline’ and pouring everything he had into it in case he never got to write for the show again (and then, when he delivered the script he was phoned a week later asking if he wanted to write something called ‘Mummy on the Orient Express’).