Anna Winston: How do you start approaching the idea of having a building as a key character in a film?

Ben Wheatley: Well, we start with a lot of drawing. I drew a set of storyboards for it, which was about 700 drawings, and then I talked to Mark Tildesley who is the production designer.

He had this image of a triangular buttress shape, and that worked for us in a lot of different ways. One of them was that it was a motif that would tie all the different spaces together in the building.

Then, because they were kind of upside down, it also gave this feeling of impinging on the space of the people, so everything was really oppressive and pushing down on them the whole time. That had come from the idea that the building itself didn't care about the people inside it.

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Anna Winston: Did you refer to the book a lot in terms of the design?

Ben Wheatley: There was the description of the development being like a hand and the towers were the fingers of the hand, and the pool wrapped around it like a pond, which was the palm. Once we started drawing it we noticed that having the towers slightly bent looked more like a hand coming out of the ground.

Then we had practical stuff. In the script there's a lot of conversations from balcony to balcony. I'd made a lot of assumptions about that and then I stayed in this hotel in Slovakia, which had a balcony – it was a kind of Brutalist hotel – and I went out on the balcony and looked up and realised that you can't have a conversation from balcony to balcony at all. It would just be little heads poking out so it'd look shit.

The idea for the fingers started to make these sloping balconies, so you could actually interact between them and it would look alright. It's a technical requirement of the script but it then starts to feed in to the aesthetic of how the building looks.

Anna Winston: From the film's point of view, architects and architecture don't come across as very friendly.

Ben Wheatley: The film is not a criticism of post-war architecture. It's not. It's not that detailed when you look at it. It's more that the building is a metaphor.

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Anna Winston: At the end, Laing seems to think about himself as almost an amenity, like he feels like he's a part of the building.

Ben Wheatley: Yes, he's like a service and he kind of subsumes himself in to it.

Anna Winston: You've previously talked about trying to find a place to recapture that idea of 70s London being a not-very-nice place to be and having to go to Belfast to find a real-world set.

Ben Wheatley: I wouldn't make that connection though, between 70s London being nasty and Belfast, which is quite the place at the moment.

Anna Winston: In London, a lot of these idealistic towers, like Trellick and Balfron, have been rehabilitated recently – there's a nostalgia about Brutalism.