Well, the first scene is you standing on your head in your underwear. I thought, ‘This is different’…

[Laughs] It was more than fun. But there’s a kind of… not assumption, but miscomprehension that doing something light and frivolous is actually easier. It’s not. It was incredibly hard work. Beth is by far the most energetic character I’ve ever played. It was exhausting. But I loved every second of it.

What are Beth’s best qualities?

The real Beth is intoxicating and there’s nothing fake about her. She has an enduring capacity to make something out of nothing. She’ll turn any situation into a positive. It’s not in that slightly sort of affected way that you come across with people who’ve read too many self-help books; she’s realistic. She has a great sense of adventure. She is utterly courageous, reckless, and exuberant.

Is there anything in you like that?

Probably. I don’t know. No, there is… If I get a bee in my bonnet about something, I will definitely go after it and not give up.

Like this role? You had to lobby fairly hard for Stephen Frears to see you…

Well, yes. It felt like one of those roles where I thought, ‘If I don’t do this, I could run the risk of being pigeonholed for the rest of my life’.

As a serious, intelligent brunette...

[Laughs] Yes. I don’t really do this [profession] to play versions of myself. I do this because I’m curious about all different ways of life.

What kind of actor are you?

It really depends. If I have any method, it’s that I’m adaptable to the circumstances. Whatever works at any given time to investigate the truth or find something interesting in the character, I will do. So that means occasionally I go full on down the rabbit hole and stay in character all day. Other times I’ll be cracking jokes before the camera rolls and behaving desperately unprofessionally. I loathe talking about it too much because I think you have to preserve a little bit of mystery. There is a weird alchemy that goes on when actors do their job and it should stay that way; a little bit magical and odd.

How do you make your decisions about what films to take?

It nearly always comes down to the role. Do I want to spend some time doing this, in this person’s head? Do I think it’s going to be interesting? Am I going to learn anything? I mean, I slightly took this job [Closed] because I thought I’m going to have time to read loads of nerdy books about the law. I’m always doing a bit of self-educating. And I love that!

So, head girl at school, Cambridge educated, it’s all true; you are a studious brunette…

I’d just like to point out that I dropped out of Cambridge! But I’ll admit; my most defining characteristic probably is that I am very curious about people and things. I like to travel; I love all those things my job makes me do. I love going to alien places and finding out about new things. And I love reading and am very studious and probably very nerdy…

This year's girl