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."

I would argue [princess] Margaret is the tragic figure of the century.

That's exactly how I felt. So getting to suddenly know this young [princess] Margaret, who had this extraordinary life - it was sad and tragic and difficult and sort of astonishing and getting to know her young self was amazing because it completely defied all my expectations.

It's this amazing combination to play, really, of somebody who's actually very fragile and hasn't really grown up properly yet - at least in a healthy environment - and has suffered immense loss with her dad - like that line where she says, [in the words of her father [King George VI], "Yes, 'Elizabeth is my pride but Margaret's my joy." She holds onto it!

My dad is a big extrovert - he's a doctor - but he always loved [William] Shakespeare and he took us to tons of theater.

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 watched tons of archive footage of princess Margaret and listened to the music she loved; that was really immersive and brilliant.