Marking the differences between them was really important. It just became second nature. When we were choosing pajamas or something, instantly you'd be able to spot: those are [princess] Margaret, those are [princess] Elizabeth. It became this sort of language, really, of the two sisters.

Some of the biographies [of princess Margaret] were really sensationalist, News of the World sorts, but they were great because they also gave first and secondhand accounts of her at home. The butlers come forward and give little moments, some of which you discard and some which ring somehow true and you use.

I started to really enjoy the fact that [princess] Margaret was an exhibitionist. Even on a day-to-day basis, Margaret's costumes were always so much more dramatic and bold than Elizabeth's were.

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

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."

[Princess Margaret] was always trying to radicalize things.

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