What was it like to play Kate, coming into this tight-knit family world of the Defoes?
As Lara, I wanted to come in and be, "I’m a big fan of the show and I really respect all your work!" - I mean, they are Olivier Award-winning actors I’ve seen on stage, and I’d worked with Nicola before, and yet, the character of Kate is not timid! So I had to give myself a talking to and go, it’s okay if you’re not terribly British walking into this set today, it won’t make you unlikeable, this is just who the character is.

Because Kate is so front-footed and it was really interesting because Deborah said to me, "darling, I think we welcome it!" I mean with Abi’s brilliant writing, you just say the bloomin’ lines and put the camera on and it just works! She’s brilliant. She’s the Stephen Sondheim of screenwriting. Abi writes all the messy, uncomfortable stuff that no-one can really articulate, and it’s delicious to play.

You're first introduced at an awkward dinner scene, was that as much fun to play as it is to watch?

It really was! Abi puts everyone in these contradictory juxtapositions. Kate arrives and has just started dating Nathan, and of course she wants to meet Hannah, the mother of Nathan’s children who he’s spent 20 years with. It’s actually really freeing to play Kate. She’s really good at her job as a critically acclaimed author. She’s totally okay with having intense, deep discussions. She’s done her own homework so she doesn’t have the baggage that Hannah has. I have no doubt that I’ll work with Nicola again because we’re going to conjure it! I think it might be something on stage…

You worked briefly with Stephen Mangan previously, on a Guys and Dolls event in London, how was it to be back together here?

It was wonderful because we didn’t have much to do with other before. I was opposite Adrian Lester on that job and Stephen was observing, narrating the abridged production, but he’s just a joy! I was slightly intimidated because I was surrounded by ridiculously clever, talented people, Stephen and Nicola were at Cambridge together – and I remember one place where we were shooting there was a piano in the waiting room, and Stephen says to me, "do you fancy a sing?" And I said "yeah!" but thinking, what’s he going to do? And he pulls up some chords on his phone and there’s me and Stephen just entertaining the green room, singing along to some random tunes!

This series continues to look at the thorny issues of women and success in terms of work vs family, do you think that’s still rarely explored well on screen?

I think I was a little bit nervous about a certain scene because I wasn’t sure if it was treading on people’s toes too much, and I think it was Nicola who said to me, "if these words were coming out of a man’s mouth, we wouldn’t think twice". So I had a talk to myself, put my big-girl pants on, and needed to be okay with being this honest and direct, and ballsy. So that’s what I did.

I could empathise with Kate’s naivety as well as her professionalism, because I remember finishing Gypsy at the Savoy Theatre (in 2016), and Imelda Staunton asking if I wanted to have children. And me going, "yeah, I think I’m going to have kids after I finish this, I think that’s the plan!"

Someone else said to me the first lesson of parenting is humility… and then Imelda and her husband came out for a Downton Abbey awards season event and we had lunch one day, and Imelda asked how I was doing, and I said "yeah, I’m not pregnant yet" And I remember Imelda saying, "oh darling it’s not on your schedule, the universe will do its thing in its own time!" So yes, there’s that first lesson of parenting!

What is it about Abi Morgan’s writing that strikes a chord and that viewers can relate to?

She’s just so real. There’s an in for everyone. We’ve probably all been in one of those characters’ situations and she’s so brilliant at writing that Stephen Sondheim-esque messy stuff. I’m going to ask her to write me a musical! She’d be brilliant at that. She’d be a brilliant lyricist because she turns things on a dime, all the time. The second you’re comfortable, as life does, it throws something at you. And she made her directorial debut on this show!