For most, the post-lockdown transition out of solitude has been a slow and tentative one. But for actress Nicola Walker, it is an experience that can only be described as jarring.

With filming for her previous project, the Bafta Award-winning crime drama Unforgotten, severely disrupted due to Covid, Walker was fully aware of the potential perils that lay ahead as shooting for the third and final series of The Split got under way.

Reprising her role as tenacious divorce lawyer Hannah Defoe in the hit BBC drama, it is a shoot that would once again see her line-up alongside on-screen husband Nathan Stern, played by Green Wing star Stephen Mangan.

But as the world around her slowly returned to normal, life on-set remained regimented.

Stringent Covid protocols meant regular testing, while strict social bubbles prolonged the actors' sense of isolation.

"I had no social life, I couldn't go out anywhere," says Walker, best known for playing intelligence officer Ruth Evershed in hit BBC series Spooks.

"You can't lose an actor for a week, it would throw the schedule into complete disarray... It just seemed impossible that anything would ever get back to normal."

However, as filming for the forthcoming series successfully came to a close, a final location shoot forced Walker into an overnight stay at a local hotel.

What the evening offered was a remarkable glimpse into the normalities of the outside world.

"I opened the doors to this hotel and it was like Alice In Wonderland," says the actress, reminiscing with a grin.

Surveying the scene in front of her, Walker recalls the unfamiliar noise and fervour as the hundred or so guests in the hotel foyer laughed, drank and merrily listened to music.

"I think I was one of the few people wearing a mask," says Walker with a laugh. "And I thought, 'Oh, I see, so this is what's really happening in the world?!'.

A series set in the midst of London's high-end divorce circuit, the witty - and at times heart-breaking - show is an examination of modern relationships and the realities and legacy of divorce.

Centred around the three Defoe sisters, Hannah (Walker), Nina (Annabel Scholey) and Rose (Fiona Button), the family of esteemed divorce lawyers is led by the matriarchal figure of Ruth Defoe (Deborah Findlay).

Created by Bafta-winning screenwriter Abi Morgan (Suffragette/River/The Iron Lady), The Split has garnered something of a cult following since series one first aired in 2018.

With series two of the drama averaging six million viewers upon its release, the long-awaited third series acts as something of a crescendo, marking the finale of the much-loved trilogy.

"As with any kind of birth, you never know entirely what the mix of DNA is going to be," says Morgan of the final series' influences.

The daughter of divorced parents herself, the creator says she's long been interested in the complex nature of separation.

It is a subject that became an "important watermark" on her own life, with the creator continuing to draw influence from her own female friendships.

Inspired by "the marriages we admire, those marriages we saw fall apart, and the marriages that surprised us" according to the writer, she says much of her material comes from conversations that take place "over a glass of wine with a girlfriend".

"It's a great way to play detective," says Morgan with a smile.

Describing The Split as like being part of "the best gang in town", Walker reflects on the series as being something of a "Trojan Horse" when it comes to subject matter.

On its surface a series about the fashionable, fast-paced lives of London lawyers, series three sees Walker's character navigating her own fraying marriage - all whilst handling the divorce proceedings of others.

"It's a Trojan Horse to talk about love and the compromises we make - the big ones and the tiny daily ones," says Walker with a nod.

"For Hannah and Nathan, those have become incrementally damaging.

"Those tiny little compromises we make day to day with someone that you love."

With the set being dismantled around them during the final days of shooting, Walker recalls her character's name plate being slowly peeled from her office door as she continued to film.

The climax fans have been waiting for, the forthcoming series also includes "one of the most excruciating scenes" Walker claims to have ever filmed.

The dinner party set-up in question, acting as the perfect illustration of Morgan's writing finesse. Uncomfortable, entirely relatable and "utterly humiliating" according to the actress, it is a story arc that has taught her "how it feels to be trapped, and for every decision you make to feel like the wrong one."

A drama that has garnered something of a cult following, series three marks the lead directorial debut of Dee Koppang O'Leary.

Graduating from second unit director on the long awaited second series of Bridgerton, as well as The Crown, O'Leary says the sheer number of women involved in the project cements it as something of a landmark in the midst of a traditionally male-dominated industry.

"It's two female directors, it's all-female producers and execs - and we have such a strong female crew. It's very much a female project through the female lens," says O'Leary.

That being said, she is quick to note how universally relatable the series remains.

"I think people expect this to be quite a female-watched show, but guys love it," says O'Leary with enthusiasm.

"Damien Molony, who plays Tyler, said that he's never been stopped by more male white van drivers and lorry drivers.

"He's always at service stations being asked 'what's happening with Nathan and Hannah then?'"

"Part of the exciting thing for me has always been the way an audience responds," agrees Morgan with a nod, describing the way in which the public can be "very nice but also very rude" in their feedback. Noting she looks forward to more conversations with strangers that begin with "I saw your show last night - I hated it", Morgan ends our conversation with a titbit of advice.

"One of the best things I heard from a divorce lawyer was 'I don't see divorce as failure, I just see some marriages as finite'," recalls the creator.

"And I suppose, if anything, this is all about trying to take the sting out of failure in divorce."

The Split, BBC1, Monday, 9pm