Ridley Scott, 2007: “Sci-fi films are as dead as westerns. There’s nothing original. We’ve seen it all before. Been there. Done that.” Five years later the 74-year-old director blusters a bit gruffly when I remind him of his death-knell speech: “Errm. Did I? I wish I hadn’t said that.” His new movie, Prometheus, is very much in the science fiction genre. So what changed his mind? “I suddenly had an idea,” said Scott about the much-hyped movie, which started life as a prequel to Alien. “No one had asked the question: who is the big guy on the chair?”

Scott is talking about the nine-foot creature (fanboys call him the Space Jockey) whose fossilised corpse is discovered by the crew in Alien, but who featured in none of its three sequels. Scott says he started wondering about the creature and its kind a few years ago. Who are they? Why are they there? “If I got underneath that, would it be enough to unearth a new story?  he said. Predictably, the more he burrowed into the new story, the less inclined he became to tie it to Alien. Now, he says, the connection is “barely in its DNA: you get it in the last seven minutes or so”.

Prometheus is set late in this century, when two archeologists (one Christian, the other atheist) discover what they believe is a clue to the origins of human life: the same cave paintings in ancient ruins in different countries. The paintings turn out to be cosmic maps, and the pair embark on a mission aboard the starship Prometheus – named after the Greek god who was punished for giving humans fire (nastily too: his liver was pecked out by an eagle every morning, only to grow back that day). So we don’t need the trailer to tell us that this meeting with our makers may not end in a warm glow of halos.

Scott comes across as every bit the Hollywood survivor: a man who’s had to fight his fair share of corners. In a career of highs (Alien, Blade Runner, Gladiator) and lows (GI Jane, A Good Year), he’s watched studios carve up his films and critics misunderstand them. “They blasted Blade Runner,” he said. “No one knew what the hell I was doing. No one got it. And then they ripped it off’. A “helmer” in the truest sense of the word, Scott steers epic tanks of movies. How does he stop them careering out of control? “By casting very strong actors,” he revealed. “I think I’m pretty good at casting. I take my time. Because everyone has to defend their island. They’ve got to be able to survive the process.”

Scott won’t call Prometheus a prequel, but he has craftily given us plenty of enticing nods to Alien, not least in the casting. Noomi Rapace, playing one half of the archeologist duo, looks every inch a heroine in the Ripley mould. Scott watched her twice as kick-ass feminist avenger Lisbeth Salander in the original The Girl with the Dragon Tattoo before meeting her. Michael Fassbender plays an android, David (the ship’s butler), and he’s the character Scott is most enthusiastic talking about. There’s a great scene, he explains, where David is pouring a drink for a tipsy crewman, who’s ribbing him about not being human. “Are David’s feelings hurt?” Scott said. “Is he pissed off? How far is he away from being dangerous?” And how far from being human, presumably – if he’s feeling human emotions? “Exactly right. And it evolves beautifully at the end.”

Androids with soul-envy – a paradox at the heart of Scott’s two modern masterpieces: Alien and Blade Runner (his most personal film: made after the death of his older brother, it’s filled with loss). Like the gods, androids are stronger and smarter than humans, yet they long for human flaws, to feel what we feel. God occupies the director’s thoughts more than he used to, says Scott, who’s an agnostic, converted from atheism. “You could have 10 scientists in this room and ask them all, who’s religious?” he said. “About three to four will put their hands up. I’ve asked these guys from NASA. And they say: When you get to the end of your theories, you come to a wall. You come to a question. Who thought up this shit?” Scott was turned off religion by his Church of England upbringing (“altar boy… terrible burgundy wine… all that stuff”). Now? “My feeling goes with “could be”.

Next up for the self-confessed workaholic is another future-set film, a Blade Runner sequel. Does he stay on top of new technology to keep up? Not massively. “I flick through Scientific American and National Geographic.