Jaime Winstone, who plays the title role and is also associate produced the grisly horror-thriller in cinemas this Friday, reveals it was easy appearing alongside him, and she soon forgot she was acting:
"There’s a scene in it where he just talks to us and tells us a story," she remembers. "And, although I was acting, me and (co-star) Aneurin became just complete kids, and I thought, 'wow, that’s how you do it.'
"I was quite nervous originally about the idea, but as soon as he stepped on set, it was just… what you do. I've been on film sets with him since I was a baby so it was just like that all over again."
Aneurin Barnard, last seen on TV in We'll Take Manhattan, adds, "It's just a case of sit back and let Mr Winstone do his job."
The film, about a bored young girl turned amateur detective after a number of mysterious happenings in a sleepy village has been a role close to Winstone (junior)'s heart for a number of years now:
"She was originally a little bit younger, but as the years went by, she became a bit more interesting. She doesn't want to grow up or face the facts of real life, she wants to live in a fantasy world. I was definitely a fantasist, made a lot of things up, followed the end of my nose... when you're younger, you just want something exciting to happen, something bigger to come along."
And so it has, for the young actress who made her name in Sucker Punch and Made in Dagenham, with a producer credit on this title as well. What was it like juggling the two roles?
"It was very hard, but we originally came up with a script, I pitched it and got it off the ground. Then I stepped back and let the directors do their thing, although there were moments… "
Fair enough - don't think anybody's going to mess, whether or not her dad's hovering in the background.
Elfie Hopkins is in UK cinemas from Friday. Both Winstones were out for the premiere earlier this week...