The Alien franchise has a history of female protagonists (Sigourney Weaver in the first four, then Noomi Rapace in Prometheus), and Katherine Waterston takes the central role in Alien: Covenant. With this film, director Ridley Scott combines the horror-movie tone of his original Alien movie with the philosophical musings of prequel Prometheus.

Michael Fassebender and Katerine Waterson at the premiere of the movieMichael Fassebender and Katerine Waterson at the premiere of the movie

"Ridley Scott gets off on terrifying the audience," Waterston says, admitting that the genre was a challenge for her. "I was wondering if it was going to be difficult to keep the anxiety level up all day. I think it may have been, with another director. But because Ridley moves so quickly, the pace on set was really energised all the time."

One thing that helped her get into the mood was the fact that most of the effects were practical, right on set instead of digitally added in later. "There weren't many green screens," she says. "My favourite stunt - you can barely even see it in the movie - I kind of go swinging off the side of this ship, and for a moment the ship is so low that I'm running on the ground, and then I get scooped back up. They just pulled me up really high and zipped me down, and I ran a few steps and I zipped back up, and it somehow felt sort of like a Buster Keaton moment or something! And that was the only day, really the only moment, where I was alone surrounded by green screen. And I didn't need to do anything, just run, so it was still in a sense a practical experience. I didn't really have to fake it."

Waterston says that Scott also made sure they knew exactly what kind of monster they were facing. "We saw images of every creature we were going to be dealing with beforehand," she says, "little puppet versions of them and stuff, and then there were amazing stuntmen who would act out a lot of it. Actually, it's very similar to how I worked on Fantastic Beasts, so that was quite familiar to me. These are directors smart enough to know the more practical stuff the actors have to deal with, the better."

When she saw the finished film, she says it had a huge effect on her. "I was terrified," she admits. "And bewildered that I could be so terrified because I had read the script, I was there on set, I knew what happens. And yet it's just a testament to Ridley's genius that he can even scare someone who knows what's coming. But honestly, I can't tolerate scary movies. I'm a real chicken!"

Watch the trailer and a clip for Alien: Covenant: