What is going on with Nina at the start of series three?
At the start of the series Nina has a five-month old daughter, Cora, so you get her trying to work out how to be a mother and a human and a lawyer as she’s gone straight back to work. She spends her time lugging around all the baby gear and she’s still wearing her heels, she will not give up her old existence!

But it’s good because it shows the struggle that a working woman has between keeping the high-powered job going and making that huge personal shift at home, sleepless nights and all! She’s getting a lot of help from Rose. She’s not drinking still, she’s sober but I wouldn’t say she’s mentally stable, I think she’s definitely still trying to work stuff out.

This series has always shown the facets of parenting; what was it that was relatable about that for you and for Nina?

Personally I went back to work on series two of The Split when my own daughter was three months old, so around the same as Nina! I was really pleased to be back at work but I think in hindsight I was a little bit bonkers. It’s such a huge shift and especially those first few months you can’t really work out who you are because you’re not the same person. You miss them and you feel guilty but you’re equally thrilled that your brain is re-firing and you’re doing the thing that makes you feel the most like you at work. So I relate to that definitely! Trying to hold on to who you were versus working out this new version of yourself.

In this final series are the Defoe sisters closer than ever before, and what have you enjoyed about that sisterly dynamic?

In this series Abi has written three quite individual journeys, I mean they can be quite self-involved women and I love how flawed they are, but they do sort of go off on their own journey - but so much happens in this series! Really huge life moments and as soon as anything happens, they all come back together tighter than ever before.

The cast just love each other, and within minutes we were all friends and that’s quite rare. But I think it does come across on screen that we all like each other and know each other really well so I’ve just enjoyed being able to work with those women! They’re excellent and they’re my really good friends.

As Nina is continuing to stay sober in series three, does it feel as if she’s got her life and career more in control?

No! She’s an addict so she’s just pushed the addiction in a different direction. I don’t think she has balance. She’s really good at her job, she’s better at being a mother than she thought she would be, and she’s trying really hard. But I’d say for most of series three she continues to be a complete car crash!

Who from the cast is most at risk from getting the giggles on set in those gorgeous office and home locations?

Fiona Button is quite good at bringing the fun to the set! But everyone is quite twinkly - Debs (Findlay) can be pretty naughty but I think we all are! Because it’s in the writing as well, we’ve got so much artistic license to mess about and we do, and we’re allowed to ad-lib so I think everybody to an extent. I always enjoy being with Stephen because he makes me hysterical, whether he’s intending to or not!

How unusual is it to ad-lib on a show like this?

It’s not normal but it’s definitely become more so because Abi has got to know us and trusts us. I know that she wrote series two and series three with our strengths in mind which is obviously amazing. She’d say, "oh you’re really good at that stuff so I’m going to give you more of that" - so that’s quite rare and I’m sad to leave that behind.

I do like a good old meltdown scene. I had that drunken dinner party annihilation scene in series one which was incredible, and Nina continues to be emotionally up and down and I love that. I thrive on that as an actor! Chuk (Iwuji) and I know each other from when we did The Bridge Project together at The Old Vic, so we spent a year together doing Shakespeare so I’ve known him a long time but we haven’t had a chance to do some big meaty scenes together, so it was really nice to get to do that.

How was the final day of filming?

I actually cried in the last take and I wasn’t meant to be crying! But I just couldn’t keep myself together. The very last take we did it was me and Nicola in a lift together and I said the last line, the lift door shut and it said ‘door closing’ and I just started weeping on Nicola! I’m absolutely devastated that it’s over. I mean it’s good, we’ve done this for five years so it’s good to move on and I will see everyone again. I’m really sad I won’t be able to be in a scene with Nicola anymore because I absolutely love working with her.