Eve Hewson is convinced Steven Spielberg and Barack Obama are in a "secret alien society" together.

The 34-year-old actress was shocked when the former US President turned up on the set of her new movie, epic sci-fi thriller Disclosure Day, to watch her and her co-stars - who include Colin Firth, Emily Blunt, Josh O'Connor and Colman Domingo - shoot scenes.

Obama's appearance on the set of the movie - which tells the story of a race to expose a huge government conspiracy regarding extra-terrestrial life - got Eve thinking that the film's director, Spielberg, who has also helmed E.T. and War of the Worlds, and Obama may have "bonded over a mutual interest".

Speaking on The Tonight Show with Jimmy Fallon, she said: "I was very curious that he came to the set with the subject matter.

"Then I was thinking about Steven, and all the things he seems to know.

"Then I thought, 'Maybe they are friends because they bond over a mutual interest.' And then I saw a video where Obama was like, 'Yeah, aliens are real.'

"My theory is that they're in this little, cute, secret alien society."

She joked: "They go camping together. They look at the stars."

Eve - who is the daughter of U2 frontman Bono - also told how she had to shoot a "crazy" scene, which featured lots of "screaming, and blood and sweat and tears", in front of former US President.

Speaking about Obama being on set, she said: "It was bonkers. We had to entertain him.

"Josh [O'Connor] was like, 'I've got to go home. I'm exhausted from being so charming.' "

Eve expected Obama to leave after he had spoken to the cast, but he stayed to watch her film a complex scene on the "biggest day" of her career.

She explained: "Steven turned to me and was like, 'You're up, kid.' I was like, 'What? But he's still here.'

"He was like, 'We have to go shoot the scene now. He's here to watch you act.'

"So, I had to do this scene, which is really complicated, but when you see the movie it's like crazy that I did this in front of Obama.

"There's loads of screaming, and blood and sweat and tears, and afterwards he [Obama] was like, 'Oh, Eve, where did you get that scream? Just stub your toe?'

"I was like, 'Yeah, man. That's what happened.' "