What happened was I was invited to meet Tom [Hardy] to discuss a project that he had in his mind about an adventurer who returns to England from Africa with secrets and with a history, and the original idea was set some 80 years later than it is now. But in the conversation I really took to the idea and I'd wanted for a while to set something in 1830 and 1840 in London, so it struck a chord.

You work, especially in the movie business more than in TV, but you have an environment where people feel obliged to have an input because that's what they do, and I think sometimes it can clutter things up and make things more problematic.

I always thought it would never happen. And then, it became possible. In between commissions, I wrote it as an original screenplay [Allied].

[Allied] got the attention of (director) Bob Zemeckis and Marion Cotillard. I'm glad I waited. If it had been made 15 years before, who knows how it would have looked, but it's got the best possible cast, director and everything. It's been fantastic. It was worth waiting.

True stories are always good because they're so odd, and so unlikely.

I find the best way to make things real is to just put two characters into a space and let them talk to each other in the way that they would talk to each other, and then see what they would say. I know it sounds weird, but that leads the plot and takes you in another direction.

In other words, when you have someone [like Ridley Scott] with that authority, then you tend to be left alone. But they were good and they're really good people, and I'm a big champion of the BBC and I think that like minds find each other and I think that FX and BBC is a perfect match.