And I think in your 40s, you land a little bit, physically and mentally, you arrive at a place where you feel you've learned some stuff. Having children at that point meant I had something very useful to do for the next 20 years.

The idea of transformation - playing something I'm not - is the bit I enjoy most about acting.

When you're making a psychological thriller, what you need to do is have an audience on shifting sand so they're never quite sure where they are.

I had this extraordinarily bizarre moment when, two Fridays ago, my missus gave birth to our second child at 11am and by the same time the following day I was sitting around a table with Ridley Scott, Russell Crowe and Leonardo DiCaprio in Rabat in Morocco, rehearsing a scene we were going to shoot the next day.

You need to try to find a way to humanize your villains. Genuine villains, in real life, still have mothers and daughters and sisters, and they fall in love. They don't walk around with a big sign saying, "Bad guy," on their head. They think they're good guys. If you can play that, I think it makes it more interesting.

Rowan Joffe is very specific. I mean, he wrote it as well and he has a very orderly writer's mind and the same applies to his directing.

Part of me was fascinated by the idea that I would only get next week's episode a week in advance and wouldn't actually know where I was going with it, until the script landed on my mat. But, part of me wanted to know what was going to happen.