The Oscar winner had to play a ruthless sharp-shooter in the new war movie but the first time she picked up a revolver it was clear she wasn't a fan - and Zemeckis had to call in an expert to give her a fast course in how to look like gun play was nothing new to her.

"Bob asked me to love the gun because he knew I hate the guns and he could see it," Marion tells WENN. "Before we started shooting I trained with the gun and I was pretty good at it. It took only one day and by the end of this I was very comfortable with the guns. I thought, 'That was it!' But I still didn't love the guns.

"I should have trained the day before I had to fire the gun on set, because I freaked out. I knew I would be discovered as a very non-lover of guns and not very good with them. Of course Bob saw it and we did one or two takes and then he came to me and said, 'OK, let's take a break. Let's take, like, 30 minutes and practice again'."

Zemeckis then asked his leading lady to use her acting skills to pretend she was a gun lover: "He said, 'I need to not see that you don't like guns, so let's pretend you like them'. I was kind of relieved that I had a little time, because I was sweating. You have to be fast and I really needed this half-hour training."

Luckily for Marion, her director was very sympathetic, admitting she had every right to worry because the vintage guns they were using in the film were far from safe.

"You're in a room setting and you're shooting blanks, but those guns are extremely dangerous," he explains. "They're firing blanks around the camera crew... and you have to be very specific where you're pointing the gun. Those guns were vintage guns. They were made very quickly and cheaply during war. They're not safe at all.

"They're very heavy. They're very dangerous. They can burn you, cut your fingers. It is very tricky... They're not toys!"