Outlander's Sam Heughan said he feared for his safety in case diagnosed psychopath Andy McNab turned on him while they were alone with guns during the making of his new film.
Sam stars in new film SAS: Red Notice - based on the Andy McNab novel of the same name - which tells the story of a small army of well trained criminals led by Laszlo Antonov who have hijacked the Eurostar deep beneath the English Channel.
Although Andy who wrote Bravo Two Zero has been labelled a 'good psychopath', Sam admits he was fearful of his safety when there were weapons around.
He told Chris Evans on Virgin radio: "We spent a lot of time doing military training down in Leeds. At one point I was with with him alone in compound with a couple of air rifles and thought if this guy turns there's nothing I can do about it."
He added: "How well can you get to know a psychopath? He is the most charming, outgoing, gregarious guy but he can tell you how to kill someone with a mobile phone or clear out a compound. It's kind of terrifying but deeply fascinating."
Sam added: "The movie is a real spectacle and at the heart of it is this character study of psychopaths."
Sam revealed he'd made the movie in Budapest which doubles for so many places and has amazing sets.
He added: "It's fine in summer but in winter it's minus whatever. Doesn't it feel a bit like a younger rougher brother of Paris with the river Danube going through it. It's stunning and everyone was kayaking and swimming."
Sam also said he prefers deep fried pizza and chips to a deep fried Mars Bar.
As he admitted to scoffing down some mini donuts with hazelnut cream filling before he could even sit down at the table, Sam said: "I have had a deep fried Mars bar but whats better is deep fried pizza and chips.
"It's a heart attack on a plate but a thing of beauty - and a bottle of Irn Bru for the full Scottish.
"I'm on Outlander at the moment shooting season six and trying to stay away from donuts and pizzas.
"Movie sets make you hungry all the time but UK movie sets are rubbish. American movie sets have omelette stations, pick and mix bars, espresso coffee and are brilliant."
Sam also briefly mentioned his new film role with Priyanka Chopra alongside Celine Dion.
He said: "I'm not sure how it happened. It's ridiculous. I'm with Priyanka Chopra and Celine Dion is in the movie and providing music too.
Yes I am in scenes with her. She's an absolute pro and a total total icon. I didn't know I was such a deep rooted Celine Dion fan. You need to let it out. It's in all of us."