PHOTO: Hannah (Nicola Walker) (Image: BBC / Sister Pictures)

Hannah has started dating again, can you talk a little bit about that – as a woman in her fifties, how is she feeling about it? It must feel a little daunting having been married for so long?

This is a new chapter in her life as a parent because when your daughter is getting married, you’re moving into a different phase. You know that awful phrase – ‘empty nest syndrome’? Hannah is getting close to the time when she will be in that house on her own. I think that she’s been very fortunate to have had amazing love in her life – from Nathan and from Christie – even though those have both collapsed. I think that means that she’s probably more likely to try again, but maybe with a little more realism – which is a shame, because I think as one gets older that does happen. I think that it’s the intimacy and the vulnerability as Hannah’s got older – it’s the idea of “do I really have the confidence and the appetite to be vulnerable with another person? Can I get on that merry-go-round again?” I think she’s really scared of that. When you’ve been physically intimate with someone for a long time, the idea of a new person…

I mean that’s why Abi is so utterly brilliant. What she writes at the end for Hannah, the scene looking out to sea, is Hannah being very, very honest – I mean I’ve not heard a woman speak like that on prime time TV before. She’s being very vulnerable, laying all her cards on the table.

Nathan’s earring – let’s discuss.

I wanted him to have a tattoo as well – a massive tattoo of Hannah on his back!

I think it’s a really good question actually – because it’s more meaningful than we imagine. Abi Morgan is a genius and what that earring is, is actually more than one thing. That’s why her writing is so great, and it’s so amazing to play her characters.

The earring is one thing when we meet it – Nathan, with an earring, what an idiot. What a late midlife crisis, utterly ridiculous, not even worth commenting (even though they are all commenting!) – I mean it’s fabulously ridiculous. It tells you everything you need to know about Nathan in the last two years in that moment. But then, it’s of course symbolic of so much more. It becomes a marker of where Nathan is, and where Hannah and Nathan are ultimately. He takes it off in the course of the two days because he doesn’t need it any more – and she lets him know she understands. There’s something deeper there, and Hannah knows it. And ultimately he does too. They’re little gifts, these character traits. They open up the whole character for you as an actor.

Two years on from the third and final series, formidable family lawyer Hannah Defoe (Nicola Walker) and her family are back and have gathered for a beautiful wedding at a magnificent vineyard, nestled in Catalonia’s wine region. The weekend will introduce audiences to a host of new characters, including Toby Stephens (Percy Jackson and the Olympians, Black Sails) as Archie Moore, and glamorous hosts Alvaro (Manu Fullola) and Valentina (Romina Cocca).

The Split is written by Abi Morgan (Eric, River, Suffragette, The Hour), directed by Giulia Gandini (Shetland), and produced by Jennie Fava (The Completely Made-Up Adventures of Dick Turpin). Executive producers are Jane Featherstone (Eric, This is Going to Hurt, Chernobyl), Lucy Dyke (The Split, Black Mirror, Ripper Street), and Abi Morgan, with Lucy Richer for the BBC. It is a SISTER and Little Chick production for BBC iPlayer and BBC One.

BBC Studios will distribute internationally and have successfully sold series one, two and three of The Split to nearly 120 territories globally as well as local format adaptations of the series in four countries including Italy and Turkey.

Both episodes of The Split: Barcelona arrive on BBC iPlayer at 6am on Sunday 29 December, and air on BBC One from 9pm that night, with episode two the following night. The first three series of The Split are available to stream on BBC iPlayer.

Watch The Split: Barcelona on BBC iPlayer from Sunday 29 December