Gavin Hood cheerfully and apologetically gestures towards my recorder: “Please edit! I talk far too much. Especially on this subject.”

We won't hold it against the South African-born auteur. There is, in the circumstances, plenty to say. His new drone warfare thriller, Eye in the Sky, is such a nail-biting watch that it's only afterwards that the viewer realises they have witnessed something like 12 Angry Men played out on a global scale.

And we mean global: as Helen Mirren’s no-nonsense colonel prepares to fire on Al-Shabaab extremists in Nairobi, she must negotiate with the British Home Office, her military superiors (notably Alan Rickman), the White House, Nevada-based USAF drone pilots (Aaron Paul and Phoebe Fox), Hawaiian imagery analysts, Kenyan ground operatives including a micro-drone operator (Barkhad Abdi), back-up troops and, lest we forget, the lawyers.

“The locations are 100 per cent accurate,” says Hood. “Creech Air Force Base in Nevada. The underground facilities at the Permanent Joint Headquarters in London. Cobra – or rather Cabinet Office Briefing Room A – is a real room in Whitehall. The image analysis unit as we call it in the film - which is really called the geo-spatial analysis unit in Pearl Harbor – they use facial recognition technology, geographical coordinates, Facebook posts, YouTube footage – anything that can be used to make a positive ID.”

Some cope, some don't
It's not surprising that Hood was immediately smitten by Guy Hibbert's textured screenplay: "I felt like you could pause on any page and have a whole discussion from every moment. Land on the drone pilots and there's a conversation about the range of personalities you find among drone pilots, how some cope, how some don't, the new forms of PTSD."

Hood has always been a politically minded artist. A law student who graduated from University of the Witwatersrand in Johannesburg during the last, dark days of apartheid, he lasted some 4½ months as a budding legal eagle before finding work as location scout for ads.

“I didn’t see a television set until I was 13 years old,” he says. “That was in 1976. It wasn’t by choice. There was no television. It was a way for the government to keep views from the outside world out. But I always acted. My parents were actors until they gave the profession up in favour of something more stable.

“So I grew up around theatre and the plays of Athol Fugard. And I had studied stills photography by correspondence during the six years I spent getting my degree and postgraduate degree. So those things all sort of came together.”

Educational dramas
At 29, he relocated to California. By night, he studied screenwriting and direction at UCLA; by day, he paid the bills with roles in The Redemption: Kickboxer 5, Project Shadowchaser II and the colonial themed mini-series Rhodes. On returning to South Africa, he took a job making educational videos for the South African department of health.

“I was hired during the HIV crisis. So for 2½ years I worked mostly in the shanty towns and the inner city, making message-driven educational dramas about Aids and HIV and prejudice and use of condoms. I had to work at speed.”

His debut feature, A Reasonable Man (1999), was a courtroom drama inspired by the trial of a herdsman who was accused of killing a one-year-old child, believing it to be an evil spirit.

The film starred Nigel Hawthorne and received good notices, but could not have prepared the filmmaker for the rapturous response given to his 2005 drama Tsotsi. The thriller about a joyrider who steals a car only to discover a baby in the back seat won an Academy Award and any number of other gongs.

"I think the big moment for us was when Tsotsi won the audience award at Toronto," says Hood. "Until then I thought we had made a little film that might – I hoped – get a following in South Africa." Independent film-maker Hollywood soon came courting with offers of mega-franchises and $150 million special-effects budgets. Hood's X-Men Origins: Wolverine earned more than $373million at the box office in 2009, but this brief dabble in the Marvelverse was not as much fun as one might suppose.

“I feel like I’ve probably over-spoken about it now, having kept it quiet for seven years,” Hood says with a laugh. “I came from the background of being an independent film-maker, with very little time for committees to discuss my work. We had to get it made, get it out and do it at a price.

“I frankly think I was ill-equipped when I got my first big studio gig. I don’t say that with any pride. I learned a great deal. I am very thankful for the experience. But I found myself working for a large corporation that owned a franchise, that wanted what it wanted and expected me to deliver.

"I did not understand that X-Men is a brand. And the studio – understandably – is protective of that brand. The director is there to deliver according to the parameters of the brand, not to direct, per se."

Eye in the Sky, accordingly, feels like a sort of homecoming.

“I’m there because I love the story and the ideas and the moral questions raised by a wonderful script. And the motivation for making the film is the same for everybody involved. It’s not a product; it’s a story we all believed was really worth telling.”

Hood, an articulate director who doesn't shy away from talking about career missteps, did not want Eye in the Sky to get pigeonholed in the way Rendition, his 2007 drama detailing the controversial CIA practice, did following its release.

American values
"Eye in the Sky is not a preaching film," he says. "It's a tricky thing. I made Rendition about waterboarding and torture at black sites operated by the CIA. And I still think those things are wrong.

“But the film simply polarised critics. People who felt that if we use torture to prevent another terrorist attack, then that’s what has to be done: they absolutely hated the film. People who more felt that allowing American values to slip would only help the other side: they thought it was a good film. With this film we are trying to bring more voices into the debate. So we wouldn’t end up preaching to the choir.”

To this end, Hood did his military-ops homework

“We did not solicit, nor did we want collaboration with any military authority for this film. The military will collaborate with you if you want to use military assets, but they will also want script approval. We didn’t want to be in that position.

“But I did approach different people in the military. What surprised me was that I found far more debate in the military than I had anticipated. There are people in the military – some are generals – who are extremely sceptical about drone warfare. Others are searching for total situational awareness. So no privacy for anyone and armed drones circling over every city in the world monitoring us.

“The question is not are drones good or bad. But how we currently employ drones: is that achieving a reduction in extremist ideology or are they adding to recruitment? The way drones have been deployed over the tribal areas of Pakistan suggests that perpetual armed surveillance of entire populations is strategically risky and potentially counterproductive.”