How does it feel to wrap up the story of The Split with this third and final series?
It’s very sad because when you get on a project with top writing, great cast, that’s really popular and people enjoy watching, you never want to let it go! You want to do it forever and let Nathan and Hannah work out if they want to be divorced for the next 30 years!

But obviously stories have a certain length that they should be, and we’ve all seen TV series that go on, and on, and on, when perhaps we’ve got it by now, and other shows that end too quickly, and I think they’ve judged this one really well. Three series was what Abi always had in mind. There are so many twists and turns in this series, it’s going to leave a big hole in my life but the time is right!

Is Nathan someone that people relate to and want to talk to you about?

I get asked all the time! Andrew Marr stopped me in the street the other day and said, "when’s The Split back?"! I was thinking, "shouldn’t you be grilling the Prime Minister?" but it’s lovely people are very invested in it. I’ve been alternately given a very hard time after the first series, and a lot more sympathy after the second series, so I’m bracing myself for whatever is going to come my way this time!

The thing I hear most about The Split is how much it makes people cry - and that’s an absolute joy to hear from my point of view, not because I’m a sadist, but because drama is all about helping people to get in touch with those things in a safe area. It’s a playground and we’re fascinated by ‘what if’ and the fact so many people are into it means that we’re hitting the truth nail on the head, responding to it and empathising. That’s great to hear.

This series sees Nathan and Hannah’s eldest daughter Liv return from being abroad, ready to marry at 18. What emotions did you feel playing those scenes?

I don’t have a daughter - I have three sons - but I have got a teenager and that thing of, you’re not worried anymore that they’re going to fall over and smack their head on the floor, you’re now worried about whether they’re going to have their heart broken or whether they’re going to make catastrophic mistakes in their lives. I can feel that anxiety already! Liv comes back and the idea that your child, because they still are your child in your eyes, suddenly decides to make a huge life decision based on what you think is a holiday fling… it’s all about learning to trust them.

With divorce on the horizon, how was acting out that new dynamic with Hannah?

I mean, after a 20-year marriage your lives are so intricately threaded together, to unpick all that is impossible. You have children together and it’s so complicated. Even in a marriage that’s doing well and is a happy one there can be an imbalance in the roles that you play as parents with your children - they treat parents in different ways - so it’s hard enough anyway! As an actor you always want to play the things that you don’t want to happen to you in real life. Bring on as much emotional trauma, awkwardness and hellishness as you can throw at me!

Is it bittersweet to wrap up your time playing Nathan to Nicola Walker’s Hannah?

It’s going to be really hard as you get really possessive over people when you’re married to them on screen! It’s like if I see Tamsin Greig married to anyone else I get annoyed, and now I’m going to feel the same with Nicola. It was just so much fun to work with her, Nicola’s a total joy, she’s so good, she’s so on it, she’s so relaxed there’s no off-screen nonsense, it’s just really good fun. As actors you define your life by these big projects, so I had the Episodes years and the Green Wing years, and now I’ll have The Split years. So I’m going to miss her and I’m going to miss the whole thing.

So this is the final series, but would you relish hanging onto Nathan for some more if you could?

Yes, I’m hoping Nathan and Christie open an antiques boutique in the Cotswolds together, selling those little porcelain shepherdesses maybe? Seriously though, yes, I know what Abi is like and if she has a story she wants to tell and thinks is worth telling then I am up for it! But she could also be in denial about it ending like we all are…