Are you excited to be revisiting A Doll's House for the third time?
I am! It's very odd, you never really expect when you say yes to a job that you will still be doing it in a year's time. But the second run [at the Young Vic] was actually very brief, it was only three weeks. And because it sold out lots of people were saying to me, "oh no we missed it", so it's lovely to have another crack. Both the first and the second run felt like unfinished business.

Will the West End production be different to the Young Vic?
The set has, give or take the odd minor tweak, remained intact – we still have the spinning house, which is a relief. I said to them, "Please don't tell me we have to do it in one room - I couldn't bear it!". And then we've had one piece of recasting because Susannah Wise [who played Kristine Linde] sadly can't come with us to the West End. But essentially it's the same production.

It must mean you get to know Nora a little bit better?
The second time we did it we'd had a really big gap since the first production, around seven months, and what that did - and I'm hoping it'll be the same this time - is it allowed me to reassess all the choices I'd made and look at the work with fresh eyes. There is something about trying to produce a show from scratch in five weeks, which is what we did originally, that means it can feel a bit manic. But assessing things from a calmer place in the knowledge that there's already something pretty solid there was just wonderful. I felt that the work deepened and became much clearer; I felt much calmer about the role.

Has your interpretation of her changed over time?
I don't think it's changed in any dramatic way. But having some time and perspective has meant that Carrie [Cracknell, director] and I have been able to go, "I think it's useful to be more contained in this moment, or calmer in that moment, so we can get the payoff there". It's about clarifying her major crisis points, stuff like that. It's about modulating the choices - the more one does it the deeper the relationships become and therefore I find it even more upsetting at the end. The stakes get higher. So I wouldn't say it's changed a huge deal, but my understanding of her has grown more detailed and deeper, I think.

You starred in an interesting short film, in which Nora was living in a London suburb. Do you think that would be her modern day equivalent?
For me, and I don't know what Carrie or Nick Payne [director and writer of the film] felt, but the idea was more about responding to the premise of the play. Obviously it was called Nora, but it was about how things have changed for women and this idea of the pursuit of happiness, about trying to lead a balanced life and how messy that is. In terms of the character, Nora is such a product of her particular upbringing. The person I portrayed in the film is such a different creature, though they may be juggling similar concerns. Nora is just so screwed up by the grooming of her upbringing, she is very extreme. In a way it would not have felt right to try and bring that personality into the modern day, it would have imbalanced what the film was trying to portray.

Hattie Morahan in <i>Nora</i>
Hattie Morahan in Nora
© Guardian

So do you think the dilemma that Nora faces – being trapped in marriage – in this day and age is being replaced by the trap of career vs family?
It's very difficult to generalise, and obviously the short film was making a comment about a very specific class, but it's a really interesting question. Both myself and Carrie, and the character in the film, are of the generation where one's mothers and grandmothers have won all these extraordinary battles. You think about how things have changed in the last 60 years and it's astonishing, but what does this mean for our happiness?

Is there still progress to be made?
Like most of my friends I was very privileged to have had a very good education and go to university, but often this means putting off having children. It's a very messy, tangled set of decisions that people have to make, that men have to make as well. But it still seems to be that, when it comes to children, the brunt of the responsibility in terms of time and commitment tends to land on the women. I think the film is saying the battles aren't won yet, there are still obstacles and inconsistencies and personal dilemmas for any woman that wants to try and juggle career and motherhood.

What do you think Simon Stephens' adaptation brought to A Doll's House?
I remember him talking about the writing of it during early rehearsals. The door was open to him, and Carrie said he could do something quite radical with it. But he implied that the more he worked with Ibsen's play the more he realised it's radical as it is. To try and ‘do a number' on it would distort what is essentially a brilliant piece of storytelling with a very radical message deliberately enveloped inside a bourgeois drawing room melodrama. So I think what he has done, which is kind of miraculous, is he's kept one foot in the 19th century - nothing that we say in the play ever feels anachronistic - and yet at the same time make it totally fresh and now. I don't know whether in ten years' time one will look at this version and go, "oh that is so 2013", but for me it's really timeless.

Looking ahead, what other roles are on your radar at the moment?
At the moment, because I'm booked up until October, there's nothing concrete. I was in a film called Summer in February which recently came out, in which I play the painter Laura Knight, who's a really fascinating character. That was a really enjoyable experience and I'd like to do more film work, but on screen it's incredibly hard to predict – it's not like theatre where you can say "I'd like to play this character and do this play one day". It's such an unknown, but then I do, weirdly, like submitting to that unknown. It can be frightening when you stop and think, ‘Oh my god, I have no idea what is coming up and I need to pay the rent.' But that sense of surprise, when it's a good surprise, is lovely.

And theatre-wise?
I suppose there are a few roles that on my deathbed, if I've managed to keep acting that long, I might say "Oh, I wish I'd played…". One is definitely Rosalind in As You Like It, and Hedda Gabler would be another interesting one. But you have to be pretty laidback as an actor and think ‘if it happens it happens' - embrace it when the time is right. If you fixate on things, that's when they're never going to happen. What will be will be. As long as the work is interesting and I'm not working with a bunch of arseholes, I'm game for anything!

A Doll's House opens to press at the Duke of York's Theatre tonight (14 August 2013)