Charlie Brooker - Inside Black Mirror

John Hillcoat:The story’s coldblooded aspect fitted like a glove with Iceland during its winter. I always feel like the environment should be equal to the main characters, because people are profoundly affected by their environment. The strange, vast and primeval landscapes with blackened soil felt like they could enhance the cruel inescapable logic of Mia’s fatal choices.

Morgan Kennedy:The countryside and the light in Iceland are stunningly beautiful, but it’s also incredibly bleak in places. Black lava fields covered in green moss, snow-covered mountains, pink skies and steam randomly pouring out of the ground. So that was where John and I were keen to pitch the tone of the film for the design. We tried to bring some of the extraordinariness of the country to our interiors.

Sanne Wohlenberg:The climate was not entirely forgiving at all times. We had a terrible snowfall while filming night shoots with the pizza van outside our hotel location. We shot that sequence over two nights. On the first night, when we shot from 6pm to 6am, we had 62 centimetres of snowfall – the biggest snowfall in Reykjavik since something like 1951! We needed to keep brushing the snow all night. During our months of prep, we’d had no snow at all, ever.

John Hillcoat:The wet snow somehow seeped through every layer of hi-tech waterproofed gear. Nothing could stop it, while special effects teams with heaters and hoses tried to melt or wash away the most crucial areas within frame just before filming. An extraordinary night for sure.

Charlie Brooker:The snowfall happened while we were shooting one way, but not the other. So we built that into the story, passing it off as a nod to the slightly fluid nature of this memory technology. Basically, we explain a continuity error that no one actually ever notices.

As the story unfolds, Mia progresses from covering up the road accident, to covering up her accidental murder of Rob, to murdering insurance investigator Shazia (Kiran Sonia Sawar) and beyond.

Sanne Wohlenberg:I hope that Mia’s downward spiral couldn’t happen to anyone! Fundamentally, it’s the story of how split-second decisions in your life can have a massive impact. When Mia was younger, she decided to go along with something that, on balance, she didn’t believe in. It was a burden on her conscience, and then when it came back, she panicked. She’d thought it might go away, but of course, in life, you have to take responsibility.

John Hillcoat:Mia’s deep inner flaw is her ambition, more than a hidden murderous rage. When all that ambition and success becomes threatened, along with her happy family, she unravels and lets her reptilian brain take over, like a cornered lizard or snake… or crocodile!

Annabel Jones:I never thought of Mia as being flawed. The idea was more to explore how you come back from having been involved in something like a terrible accident. I think it was all about that one incident, after which Mia tried to protect a friend. That was the start, so it’s less about her being flawed, and more the horrible logical inevitability.

John Hillcoat:The killing of Rob was almost more like manslaughter, in that it was not premeditated or calculated. Mia was trying to stop him in the heat of the moment. Even once on the ground, he yanks her hair, which has her counter by choking him too much. It all goes too far.

Charlie Brooker:Obviously, the point at which Mia really turns is when she’s hiding Rob’s body. What she should have done, when he’s dead in the hotel room, was call the police and tell them there’d been an accident.

Sanne Wohlenberg:Mia takes one step, then another, and eventually there’s no turning back for her. You end up going, “Oh my good lord, surely not!”

Charlie Brooker:When she’s killing Shazia in the shed, there’s no going back. Once that happens, it’s Nowheresville for her. And then, once she’s killed one person, she keeps upping the stakes for herself. She’s got to keep killing people to cover her trail.

Andrea’s performance is really interesting, because Mia isn’t some wild-eyed, panicking maniac. When I was writing, I probably pictured somebody sweatily running around the hotel room going “Argh! Argh!” – much more like William H. Macy in Fargo .

John Hillcoat:Andrea was incredible in her ability to channel the most traumatic of states. She could become super-focused within a nanosecond. Her mood would change from day to day, depending upon where her character was heading, but she could still discuss anything at any given point. During the first rehearsal, she threw herself into things so forcefully that she bruised half her ribcage. Despite being in agony for the rest of the shoot, she miraculously maintained her razor-sharp instincts.

Sanne Wohlenberg:Andrea’s a very focused actress. She had a hard-hitting part to play emotionally, which was difficult. Like anybody who immerses themselves in a part, there were days when she was more withdrawn, and other days, when the scenes were lighter, less so. But she was lovely to work with.

Kiran was very thoughtful and modest as Shazia, a bright light in the story. Her horrendous murder scene in the remote shed was a traumatic experience for all involved. No one wanted her to die, especially like that. Kiran was in a complete state all day, shaking like a leaf first thing in the morning and crying for real all day long. Yet she still managed to listen carefully and work with us all. Much later, when showing her the finished episode, it was the one scene she simply could not watch. I completely understood. I can’t watch it anymore either!

Mia’s descent reaches its lowest point when she kills Shazia’s baby son, who turns out to be blind. This murder has, however, been witnessed by the family’s pet guinea pig.

Charlie Brooker:Of course, the very end is quite a gag. People either go with that or they don’t, so it’s a really interesting one. The fact it’s a blind baby – and it sounds weird to say this – was part of the joke.

‘I’m really sorry. Will you please close your eyes for me?’

Annabel Jones:It’s harder to land that comic ending, when tonally you’ve been much straighter all the way through. So I can see why some people find it a jolt. Whereas if the tone had been Fargo -esque all the way through, the ending might have been less of a surprise.

Charlie Brooker:The fact that she needn’t have killed the baby because it was blind, it’s like, “Fucking hell.” There was debate about that, and when I sent the first draft I even included some kind of caveat, because I thought everyone would say no.