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

Everybody has an image of [princess Margaret], to a certain extent. But I felt it would have been harder if we were playing them as they are now. In a way, I don't know how much of a living memory we as a collective have of them in the '50s, when Margaret was 21 and this sort of Elizabeth Taylor. You don't think of your grandparents as being teenagers. You just can't - your brain just can't go there!

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

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.

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.

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.