The Knockturnal attended the special preview screening and Q&A with Brady Corbet and Mona Fastvold at the IFC Center on 20 July 2016.  Below is an extract from the Q&A (there is no mention of Robert, but the article is a great read):
So what was the actual shoot like? Where did you shoot? How long was the shoot?
BC: It was 24 days in Hungary. We shot in Hungary for two reasons, one was that to shoot in France with a child is virtually impossible because you can only have three hours with the child per day, so obviously that didn’t work for us. And then the other reason was there was not just a film lab, but two film labs. That meant that we could shoot on celluloid and it would not be particularly expensive.
The child that you mentioned [the film’s young lead, Tom Sweet], how did you cast him and was he the first character you felt like you needed to cast?
BC: Actually he was the last character we felt we could cast because kids grow so fast and the movie was constantly falling apart, so we had to cast him just about three and a half months before we knew the film was actually happening, because we thought the film was actually happening many many times before it was actually ready to go in terms of all of the money being released, so we cast him last. And our casting director spotted him on a soccer field playing soccer and then we saw him and we knew.
…
BC: The music was made by a guy named Scott Walker, who is a very, very, very brilliant composer and pop artist, and I still think its appropriate to call him a pop artist because he still actually makes very melodic music. He used to write and sing ballads, which he no longer does. But he kind of constructs songs now as if they’re three acts and so the idea was that we would hire someone, he had written a lot of music on themes of tyranny, and we thought that would be an interesting element to incorporate. And then also because we knew what the scope of what we would be able to pull off visually, that we needed something to counteract that aurally, so we decided to hire someone that would make something gargantuan
What was the process like? Was he already composing from a script stage or did he compose after he saw a first cut of the film.
BC: He started the overture from the script stage, so that was the sound of the film. And then he built on that for a year and a half and developed the 36 minutes of music that’s in the film.
How did you find this cinematographer to bring this story to this life?
BC: There were several different cinematographers that were attached to the project, because the film was supposed to happen I guess three or four times and then Lol [Crawley] actually came on board very late in the process and he is very intuitive, so basically he didn’t arrive with a million ideas, he arrived and he reacted to the space. The space was extraordinary, because our designer Jean-Vincent Puzos was a really particularly great designer and we were talking a lot about doing sort of like Anselm Kiefer, but Victorian style or something. The walls would look like they were sprayed in acid or something. And Lol is just a really soulful guy. We’re both like, him especially, he’s really a working class personality and so there’s nothing pretentious about it. We’d go in and we’d try and find the most beautiful shaft of light that existed and if there wasn’t enough light for us to use it then we would try to recreate it in a way that would sort of emulate what we saw when we walked on to the set.
The Q&A covers topics such as working with Berenice Bejo (who I adore in this film), what it is like for Mona and Brady to collaborate and what projects they have coming up next *fingerscrossedpleaseRobertdoesanothercameo*.  Click on the link above to read the full article.