You're in a very nice position as an actor when you're portraying a piece of history that actually happened and portraying characters that actually existed. There's so much more to draw on and your research as an actor becomes much easier than if it's some fiction that you're trying to create a world around and background and history.

It's funny when you know you're playing two characters and you're aware of how you have to play each one into your performance of the other. You're constantly at the back of your mind thinking and it all gets a bit confusing.

Most of the crew were staying in Monaco. But my family and I were actually staying in Nice because I had my whole family there and we wanted a little more space and to stay in a hotel. The truth is we were asleep [when the attack Bastille Day terror happened] and woke up the next morning to it and it was obviously horrific. And then the idea of going out and filming, it just felt so stupid to be working the next day and pretending that everything's cool when you're making some frivolous thing.

I think you've really got to cling to what makes sense to you. Obviously, I'm not a serial murderer in my real life, so that's where you have to delve into and do all the research. But, you have to find something likable in the character.

I'm probably the worst person for 'Men's Health' to interview.

Jamie Foley - he's a very different energy to [director] Sam [Taylor-Johnson]. The whole experience was actually quite different.

It's not like I cleaned up with girls. I always looked young and I was very small; I hated being 'cute.'