A bit of a change from the usual in this week's collection of interesting facts around the latest episode of Doctor Who. We have writer Mark Gatiss's insider version of events, complete with nods to classic Who, references to old songs, and the reason why there was no credit sequence.

And being a natural raconteur, he gave us more than our usual 10 things, which is hardly a cause for complaint:

1. The idea comes from a very personal place:

"I've had it in mind for a long time. I've never done one set in the future. And I'm very interested in insomnia. I'm slightly insomniac. Actually, I'm a lot better than I used to be. I used to be terrible, terribly bad. Those moments spent looking up at the ceiling... and I read this article about how essentially the pressure we're all under these days to be permanently working is only going to get worse.

"So I thought if in the far future, what if they found a way of eliminating sleep altogether. They will. And something Doctor Who hasn't done for a really long time is satire, really. And the best possible vehicle for satire is science fiction because you can imagine a world based on concept that you can have fun with, so that was the essential idea."

2. The story was originally longer, and you can tell from some of the references in the script:

"It was going to be a two-parter. Essentially what happened is that all the backstory that was going to be throughout the two-parter got crunched down, so it's there. But I feel like it's good because it's the best possible way of doing it. I did all of the work, but it's only there very lightly.

"So in Neptune, around Neptune, they are actually from Triton, which is the chief moon where there is a colony where there are all of these cities, and they've developed a thing called the Morpheus process, which reduces sleep to five-minute bursts, and you can work a week without sleeping. There are people who go for it who are known as the Wide-Awakes, and they're like the thrusting executives. They are the people who'd take cocaine. And then there are sort of refuseniks, who they would refer to as the Rips, the Rip Van Winkles. They don't want to give up their sleep. It's literally all we've got left. So that was the whole idea the sort of two factions.

"And it's all there in the existing script, but instead they sort of throw away references rather than a fully worked-out thing. And then I had this idea. Two things I thought, at Steven's encouragement, I said I'll write this as a horror film, as it were going to be a movie. And then I'd rein back, and I kind of didn't. And then I had the found footage idea, and that's why it became a single because I don't think it could sustain it over two. That was the reason behind that."

3. There is no credit sequence because the episode is Rassmussen's film of events:

"It's amazingly handy because essentially we had all of these conversations. Well, we can't really have any music in it because it's not like that. It's a P.O.V. thing. That was the twist. But we had to make a decision. It's still Saturday night Doctor Who. You can't make it like a pitch-black horror film. And Steven kept saying, quite rightly, that let's remind people all of the time that they are seeing different viewpoints. Otherwise, it'll look like a very badly shot episode of Doctor Who. But the great get-out is that Rassmussen is ultimately making a film. He is making a film, and I was very particular about this.

"The first thing he says against the black is 'You must not watch this,' which, of course, is an invitation to watch. But it turns out that he is putting all of this footage together deliberately to put that glitch in people's eyes and spread the Sandman. In the end, it kind of gets you out of all kinds of holes because there is a bit of music in there. There is a bit of fiddling about. It all makes sense because ultimately he is pulling the strings. It's not an intentional metaphor because it is like sitting there and authoring your own episode."

4. The Silurians can't have named themselves Silurians:

[This is a reference to the common observation that several of the races in Doctor Who are given names based on where (or when) they are from, or where they were found, rather than the names they might give themselves]

"There’s a particular thing Clara suddenly says, 'Because of the Sandmen.' And [The Doctor's] like, 'What?' And she says, 'The Sandmen after the song.' And he says, 'I do the naming around here. It's like the Silurians all over again.' That's because it's a thing over the years like the Silurians are called the Silurians even though it's the wrong time [they're actually from an era between the Silurian and Eocene Periods]. And Ice Warriors aren't really the Ice Warriors; they're Martians, but they are the Ice Warriors. So I thought I'm just going to get in early. Let's give them a name now because otherwise they'd be called the Rassmussen mutations or something. They're called the Sandmen! That's what they're called."

5. Their name also comes from the song by the Chordettes:

https://www.youtube.com/watch?v=oNuX7bs2qAM

The reason for 'Mr. Sandman' is I've always been in love with that song. It's very creepy, I think. Particularly, Russell T Davies talked to me about using it, and it was in the early drafts of 'The Idiot’s Lantern,' my second episode of Doctor Who all those years ago. And Russell said, 'There's something so weird about this song. It’s so chirpy but it's so creepy.' And it is, isn't it? It's a bit like Santa Claus. He sees you when you're sleeping. There's something a bit odd about it, and I've always loved that, and I thought, when things were coming together, I thought for this episode, that would be perfect, and again, the chirpiness of it. There's a lovely bit at the end where Rassmussen is shot, and you hear the music carrying on in the background. It's really eerie."

6. The Sandmen are in a fine tradition of Doctor Who monsters based on unexplained questions from childhood:

"It's that thing that Steven describes so brilliantly of childhood fears. The Weeping Angels are really that game Grandmother's Footsteps. People creeping up behind you, cracks in the pavement. Really mythic things we're always had. And I just suddenly thought one day, what if that [points to the sleep in his eye] isn't passive. And I thought well that's a great idea or a creepy idea because we all do it. We wake up and wipe the sleep out of your eyes, but it's actually for a reason. You do it and it goes. If you left it because you don't sleep, it might become a Sandman."

7. It's fun to imagine how the geopolitical balance of power will have shifted in the future:

"The undisputed greatest Doctor Who writer was this guy called Robert Holmes, who wrote "The Talons of Weng-Chiang." He had this brilliant gift, particularly in that story, for what he called opening a window onto a different reality. And in that story, there are so many brilliant jokes. The Doctor thinks he's fighting this 19th century villain, but he's actually from the 51st century. And he’s come back in time through this evil time experiment. He has to absorb the life energy of people to survive. But he's from a different world, a different time. And all the Doctor says, casually, 'he nearly started World War VI.' Brilliant! Not World War IV or World War III, World War VI! So clever.

"And then it turns out that this man is named Magnus Greel, the Australian Minister of Justice. And the Doctor says, 'Of course, I know who he is. I was with the Filipino army during the last advance on Reykjavik.' And I remember as a child going, 'What does that mean?' It's a fantastic imagined future in which the Philippines and Iceland are the major power blocs in the world. Isn't that brilliant? People talked about it for years, but it's a stroke of absolute genius lightly done.

"So I've always thought it would be nice to just fiddle with things, and quite simply last year I was in Japan and India. And I loved both cultures and both experiences, so I thought, I don't know what happens in the 30th century. Maybe what happens is that Japan and India merge after the Great Catastrophe. It doesn't have to be a hard-and-fast rule; maybe it only lasted a century. I thought it would be great to have a very different source of cast as well. The look of the ship is different; it's very Oriental. And it's predominately Japanese, Chinese, and Indian actors, and you immediately just get a flavor of a different time. 'Some things happened,' the Doctor says, which is a reference to another great story called 'Frontios' [in which there's a description of a collision between the Sun and the Earth]—the Great Catastrophe. So I said that's what happened."

8. Mark wrote Rassmussen specifically for Reece Shearsmith:

"I wrote it for Reece. He's been badgering me for years. Of course, he played Patrick Troughton in An Adventure in Space and Time. So I said to him, 'You’ve done very well, you know. You've played the Doctor, and now you’re in this [episode].' He always wanted to be in Doctor Who, and I thought this is the perfect one because, it's that thing, we've got such a shorthand between us. You don't even have to think about it. I knew he would know immediately how to play this part, and he did. It's a sort of a moral coward. Of course, there's a twist to it so it's not quite what it appears to be."

9. The character of 474 is based on Tonto from The Lone Ranger.

"It's Tonto, isn't it? I was originally thinking of Lenny in Of Mice and Men. The sort of good-natured idiot is a character we've had forever. The sort of idiot-savant, that's what she's like. She's bred for war, but unexpectedly is in love with this other soldier because she thinks he’s pretty, and he hates it. But I love this idea of this sort of lumbering soldier who is sort of simple. And then when Clara finds out that she's a clone, and they’re just breeding them for war, that's what the tattoo is. She’s just been stamped with it in the factory."

10. Some Doctor Who stories are more collaborative than others:

"As ever, sometimes in terms of a remit, sometimes it's quite prescriptive, sometimes it's not. I pitched this story several years ago, and Steven finally said, 'We're going to do the dust one.' And that's all it was really, whereas last year, Steven asked, 'What if the Doctor meets Robin Hood?' [for 'Robot of Sherwood']. 'The Crimson Horror' was actually a bit of a shopping list of things. Sometimes it's quite prescriptive, sometimes it's quite free."

11. He tries to keep clear of the big season story arcs if possible:

"I try to stay away from things as much as possible because I don't want to be spoiled. I love just watching it as it goes out, so unless it directly affects me I don't want to know. The only real way it affecting mine, coming up as Episode 9, Steven said that Clara needs to be very self-confident. She's almost like the Doctor. She's sort of doing it all herself; she's seen all of this now. She's not frightened in the same way because this builds into something. I said I didn't want to know what it is."

12. The ending is supposed to be left open:

"I don’t think the Doctor should win all of the time. He shouldn't, because life's like that. He's the hero, and we want things to be wrapped up, but I think it's quite nice if it's ambiguous. He knows something is wrong. He leaves thinking, 'This doesn’t make any sense.' That's also a get-out-of-jail card. There are going to be consequences because if Rassmussen succeeds, pressing that button, then it’s going to spread. So maybe there's a sequel..."

13. The title comes from Shakespeare's Macbeth:

"The episode was originally going to be called 'The Arms of Morpheus,' which, of course, is a classical allusion. He was the god of dreams. But then I thought... we had kind of forgotten about the Punchdrunk show Sleep No More [a 2011 Broadway production by British theater company Punchdrunk]. But Macbeth is my second favorite Shakespeare. I've always loved it.

"It's just a wonderful title, isn’t it? It tells you what the episode is about, which is sort of an unusual thing. You don’t have to struggle, call it 'Invasion of the Sandmen.' It's what the episode is about, so I thought that was rather cool. But then, I remember Steven and Brian rang me up. I was just doing a play at the National Theatre, and they rang me up, and they had hardly any notes. But Steven said, 'I want you to give it a sort of mythic dimension.' And all this became was one little speech from the Doctor where he talks about what sleep is. And obviously the perfect thing to quote there was the Shakespeare. It all ties together.

"The Doctor says it's essential to every sentient being in the universe, but to humans, you stupid dirty needy humans, it's a commodity to be bartered away. And he says the poets were right, the ancients were right. It's beautiful, it's important. Most importantly because it keeps the monsters away. So that’s where that came from. Plus, I had this thing from the beginning. It was really one of the first ideas, was that somehow, even though it's a very frightening episode, the ultimate message to children is 'Go to sleep.' Not stay awake. And I hope parents will forgive us."

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