Actress Gugu Mbatha-Raw revealed that, like her human ambassador counterpart Barclay Piere-Dupont (Russell Tovey) in the Doctor Who spin-off The War Between the Land and the Sea, her character Salt is a parent.

“She’s a warrior. She’s a mother. She’s an ambassador, and she has a very regal presence,” Mbatha-Raw told Radio Times. She’s a fierce protector of her species, and she meets Barclay in this negotiation process to defend the rights of her people who have been under the sea for many years, dormant, until now.”

“I’ve never done such a large- scale creature-character. I thought it would be a really interesting acting challenge, physically. Without spoiling too much of the magic, I spent three hours in hair and make-up every morning with Georgia Brown and Samantha Di Giuseppe. It’s quite a surreal experience as an actor, I think, to look in a mirror and almost not recognise yourself. You’re liberated from all the usual tools you have. Suddenly you don’t have curly hair and brown skin. You’re free to create something completely different. You have what you bring: your face, your physicality.”

“Salt is a part of a species that lives under the sea that have been dormant for many years called Homo Amphibia,” Mbatha-Raw explained in a BBC press release. “We initially meet her because she has come to represent her species as an ambassador, to defend their rights, and expose the human race for what they have done to the oceans. She’s quite a fearsome character. She comes with a posse of a Homo Aqua and other species from the sea, and they’re incredibly intelligent. I think what I’ve loved throughout the series is that you get to see so many different sides of her. She is in this ambassadorial role and has this formal and regal quality to her, and as the series goes on, she becomes more human.”

“It’s not every day that you get a character that is so liberated from your usual look. You have to discover a different way to move, a different way to speak, and it was a really fun challenge.”

In the series, a diplomatic contingent which includes Barclay travels to Salt’s underwater realm.

“One of my favourite sets was under the ocean in Salt’s domain. Everything else up until that point, Salt is out of her comfort zone in the human world and breathing human air. Stepping onto that set really transported you to another world.”

The series will explore how Salt and Barclay’s relationship becomes the beating heart of the series — how that connection blossoms and becomes something incredibly important for them personally, but also the implications that has for the planet.

“I would say they are soulmates from totally different worlds,” Tovey explained in a BBC press release. “and unbeknownst to them, they’ve been thrust together. It feels kismet or astrological — the universe has made these two connect in the most profound way and it’s affected the planet.”

“It’s really an interesting and epic love story,” Mbatha-Raw added. They initially meet in a professional way, and I think for Salt she feels like she has been othered and ostracized by most of the human race. [Barclay’s] really the first person that sees the Homo Aqua and Homo Amphibia and gives them a sense of humanity and respect. I think that is where their connection grows from. It becomes this beautiful journey of trust, him going into her world and liberating her to be more playful and multifaceted.”

Tovey further described the relationship to TV & Satellite Week.

“[Barlcay is] not prepared for any of this. He doesn’t understand why he’s been chosen, but as the show goes on, Salt allows him to understand himself more and creates this amazing bond between the two of them that becomes so fundamental for the planet, but so deeply intimate and personal as well.”

“[What Gugu] does with the character is mind-blowing. Gugu would turn up on set as Salt and there was just an instant reverence to her – she commanded the room.”

Written by Russell T Davies and Pete McTighe and directed by Dylan Holmes Williams, The War Between the Land and the Sea will begin transmission on BBC iPlayer and BBC One in the UK on 7 December 2025. The spin-off series will transmit exclusively on Disney+ outside of the UK (where available) some time in 2026.