A genius filmmakers has a brilliant idea. But there are problems: it’s going to cost untold millions of dollars to realize, and he has no clue how to make it happen. Enter a great producer.

This is what happened with Alfonso Cuaron‘s latest film, Gravity. From the outset, the small space-set movie was incredibly ambitious. No one knew exactly how to make it feel and look like the action was happening in space. So even with two A-list stars attached, the movie was a gamble. It took the watchful eye of a man Warner Bros. truly trusted. That man was David Heyman, the producer primarily responsible for bringing a little franchise called Harry Potter to the studio and making them billions. He’d previously worked with Cuaron on Harry Potter and the Prisoner of Azkaban and was Cuaron’s first phone call when looking for someone to help make his near impossible vision a reality.

/Film had the opportunity to speak to Heyman about this gargantuan task. We asked how Cuaron approached him, how he approached the studio, how you budget a film that is literally inventing technology and what one tiny change took two and half months right under the wire. Check it out below.

/Film: What was the first pitch for the movie like?

Well he didn’t really have to pitch. He said, “Do you want to work on this film? Do you want to produce it?” There was not a moment’s hesitation, because I have worked with him before. I have loved his films that I’ve not been involved with as well as the one that I had, and it’s a privilege. As a producer, you want to work with great directors. You can’t make a good film without a good director and you can’t make a great film without working with a great director. I think Alfonso is a great director. [Grabs a menu from the table] I would make this menu with Alfonso, because he is a genius. It’s not easy, because he’s really demanding and he expects the best from everyone, but you have the potential to be part of something that’s extraordinary and he makes everybody around him better at what they do. So that was the first thing, then he gave me the script, and the script was superb. It was very lean. He and Jonas, his son, had written it, but it was very lean. There was nothing extraneous, but what I love about Alfonso’s work; it works on multiple planes. Yes, it’s an action adventure film, but it’s also a very human story. It’s a woman’s journey. So that’s the second love, and then the third love is the thematic richness of adversity with birth and rebirth, which is obviously very connected to the character. With Alfonso, those ideas are conveyed and the humanity is conveyed not through dialog, but through images. He’s a visionary and so that was clear in the script that it was going to be something special. Then we began to talk about how we were going to do it and that’s when you go “Holy…”

Is it difficult to approach the studio with this script, the idea that it takes place in space, and a female lead?

Yeah, but to give the studio credit, Warner Bros. is a good studio. I’ve been there for a long time and they’re brave. They give Batman to Chris Nolan. They believe in directors… I mean that might not seem brave now, but at the time that was a big leap. They allowed me to bring Alfonso on to do the third Harry Potter after Y Tu Mama. They brought in David Yates, who had made TV, to do the fifth film… So they believe in filmmakers and they support their filmmakers. In fact, they are most interested in filmmakers, so they got it. It wasn’t without it’s dance. The film, when you are working on this budget, there are certain things like you have to have a star, but they were incredibly supportive all the way through. So yeah, it is an extraordinary, as you said, action movie in space, ninety minutes with a woman lead and one character for an hour plus of the film, but they bought into it, because they believe in Alfonso. I don’t know if it’s from Harry Potter, but it may be. (Laughs) It didn’t hurt.

With this movie you had to invent new technology — we know all about the boxes and stuff — so how do you budget for that?

That’s a really good question. It was a moving beast, because we didn’t know. We knew that, and again to give the studio their credit, they were spending a fair bit of money while we were out there trying to figure out how we were going to do this. (Laughs) But they were our partners. Chris DeFaria, who runs visual effects at the studio, was very much our partner and he was the person who said initially “Well, you can do this all on an office chair with a light and a camera.” We didn’t end up with the office chair and when we showed him it couldn’t work he bought it, but he was the person who said “The camera needs to move, not the actor” and that was a really significant moment in the process. But budgeting? You have an overall budget. You don’t know… You have an R&D budget. There weren’t many sets, so in a way part of it was the money that was in sets would get moved over to the money for R&D, but the money came from everywhere.

And also, because of the fact that you’re so locked into these elaborate visual effects, there wasn’t a lot of room for improvisation, right?

No. You say that and you’re right. It was a very rigorous shoot and the movements the actors could do were always confined, because every shot connects to the next. Like “Here on second two, there on second ten, there on second twenty-three.” That was very prescribed with the arms being the same. But Alfonso would find a way to improvise with the visual effects, which was amazing. We made a previz which was the whole movie and yet once we were in post, by putting a helmet which would cover something, he would be able to change things. It was amazing. Even down to the fact we finished the film for all but sound, which we ended up doing in July the Dolby Atmos, we finished in March. We were done. Then Alfonso looked at the film and he said, “Damn it!” What happened was the craft in the first two minutes of the film, the craft was the right way up. But in space there is no up and down So he thought “That’s ridiculous. Let’s, in the first image, show what world we’re in.” So he wanted to flip it and I mean he’s been working on this film for four years. He wanted to flip it, because he had an idea how to make it better and we did it. That took two and a half months to do, that one shot. But it’s reflective of him, which is he’s never settling, he’s always pushing. He’s always exploring and he’s improvising and making things better.

Reviews out of Venice and Toronto were great, and Jim Cameron calls Gravity “the best movie space movie he’s ever seen.” Does that all set expectations that are impossible to match?

That is a danger of course. You don’t want people to be disappointed, but it’s really nice. It’s a relief more than it is anything else, because you’re in the bubble. You have no idea and I knew it was special, but “forests… trees…” you can’t really see anything and also you’re always trying to make it better and aware of things you want to tweak. Like Alfonso with that shot. There’s that line where someone says “You don’t finish a film, you let it go” and I think that’s true. So you’re always aware of those things that if you had another year you could do. Listen, it’s fantastic. It’s a little scary, you’re right because of expectation, but I’d most certainly have this rather than the other.

In the press conference you said you didn’t want to comment on specifics of the new Harry Potter films. [NOTE – It was later revealed will be producing Fantastic Beasts and Where To Find Them] But as the person who brought the rights to Warner Bros., did you ever think once you closed that seventh book that we would see more movies in this world?

I don’t know about movies, but I thought that Jo might write something else, because she knows the world, loves the world, and hence why she is writing this new thing. So no, I most certainly didn’t expect there to be a film, but I’m happy that there is.

Gravity opens everywhere October 4. See it on the biggest screen possible.