It was always said you couldn't have two sisters less alike. In a way [princess] Elizabeth was always internalizing everything and [princess] Margaret was always externalizing everything, so that became the basis. The storyline becomes about these two sisters: they're fighting for their position or trying to establish their identity in the world alongside each other and in relation to this establishment which only those two were a part of.

I did a lot before [being cast] because I knew how important it would be for playing somebody real, or attempting to - to show the team [the role] was something I would be fascinated to do. I read a couple of biographies and I watched everything I could find [about princess Margaret].

[Queen Elizabeth] is just the granny queen! She's our granny queen who shakes people's hands!

[Princess Margaret] was always trying to radicalize things.

I knew she was a party girl. The book I liked most on her was called [princess] Margaret: A Life of Contrasts and getting to know her, it was how conflicted her position and her internal life - or self - was. She is so fiercely royal and so fiercely "sister of the queen" or "daughter of the king" because that is her identity and it's all she's ever known. And at the same time she is struggling to push the boundaries and to break away from it, to be different or to modernize the monarchy, to turn it on its head.

I still get stage fright horribly. I still get nervous. I do tend to find when you're playing characters, often - just for the time you're playing them - there are sides of your personality that get stronger because you draw on them more.

I remember somebody saying something to me about Frost/Nixon, when Anthony Hopkins does his famous speech, and the difference in the way Anthony did it was to dramatize, essentially, what was a documentary-style version of that speech. I remember someone saying to me, "There is artistic liberty."