Did you also shoot in real London Underground tunnels?

Payne: We did. I think one of the things that people don’t realize is the network of tunnels that exist underneath our feet in London is quite extensive and extraordinary. The amount of ghost tunnels that when we’re on the Tube, and of course they’re not lit, we can’t see them. That when we go down our normal, ordinary everyday Tube commute, we will pass a number of ghost tunnels. And again, TfL [Transport for London], we’re all lucky that they’re fans of “Luther.” They’ve helped “Luther” along the way in difficult locations all the way through the series. So they were willing to open up the tunnels and let us film in there.

And let me tell you, there was a moment when I was talking about the sequence and Neil and I went down. It was just Neil and I down in these ghostly tunnels, those sounds and those shadows. Now I’d been down there a few times before, but watching Neil react to this space afresh really reminded me [of] the thing that Neil talks about a lot. He writes this incredible primal fear into these stories because it’s what he feels. It’s not what he wants people to feel. It’s how he feels. And I got a chance to stand in those spaces with Neil, which is something I won’t forget, let me tell you.

Cross: Jamie, my friend, is calling me a chicken on camera.

Payne: No, I’m not!

Cross: Right in public, calling me a coward. But he is, of course, entirely correct.

That’s another thing it has in common with “American Werewolf.” Because that movie has the big sequence in the London Underground.

Payne: Oh yeah.

Cross: Of course.

Payne: Now can I tell you something about that? “American Werewolf in London,” there’s a shot that I stole or was inspired by. I don’t think I’ve ever admitted it to Neil, but Neil will say I noticed.

Cross: In season 5.

Payne: In season 5, on the bus in that terrifying sequence where the lady alone on a night bus is attacked. There’s a shot where you could see our killer come in at the bottom of frame and crawl in. And that was absolutely stolen from “American Werewolf in London.”

I think as long as it looks good, there’s nothing wrong with stealing. There’s that shot in [season 3] that’s very “Suspiria,” where the guy’s head gets shoved through the ceiling.

Payne: Yeah.

Cross: Oh well, as long as these things are done with love, that’s the key thing. And one of the things that kind of animates both Jamie and me is that we’re fans of stuff. And there’s cynical theft, there’s theft which arises from creative bankruptcy. And there’s like the Beatles playing Chuck Berry. It’s a function of love.

Yeah, like an homage. 

Cross: Yeah. It’s not even that. It’s just it’s so cool, it’s just a fun thing to do.

Speaking of being fans of stuff, how did you balance bringing stuff that the fans could enjoy, and then also making this film accessible for newcomers who’d never watched an episode of “Luther”?

Cross: I wish I could look you in the eye and tell you that I knew how to do that. But the truth, it was extraordinarily difficult.

Payne: Yeah, it was a daily obsession, seriously, about how to do both those things. I think it was the banner headline over every single day that we had in production and in post. Literally, we only finished the film X amount of weeks ago and I think that conversation carried on. Because it was essential to do both. It was essential to have a standalone film that could bring in a new audience, but it was also essential that the audience that had been so loyal for so long, that they felt that this was a continuation of the story. We had to achieve both those things or we’d have failed.