Russell T Davies says Doctor Who spin-off takes a darker, environmental turn

The War Between the Land and the Sea explores humanity’s response to an ancient species rising from ocean

BBC’s latest Doctor Who spin-off, The War Between the Land and the Sea, has launched with a “tougher tone,” according to writer Russell T Davies. Produced by Bad Wolf, the five-part science fiction series debuted on 7 December, featuring extensive underwater sets and filming primarily in Cardiff, with additional locations across Wales.

The story follows UNIT employee Barclay, played by Russell Tovey, whose ordinary life is upended when an ancient species emerges from the sea, triggering a global crisis. Gugu Mbatha-Raw stars as the mysterious Salt, who surfaces during a Thames summit, while Jemma Redgrave reprises her role as Kate Lethbridge-Stewart, UNIT’s leader, struggling to maintain order amid chaos.

Davies explained that the series was inspired by his environmental concerns and his love of the sea, aiming to explore how humanity copes in the absence of the Doctor’s “safety net.” The narrative pushes characters to their limits, blending monsters, romance, chases, and gunfights into a “properly entertaining thriller.”

The creative team consulted geneticists and revisited Doctor Who lore, including the Sea Devils and the concept of Homo Aqua, a species that could have branched off from humans millions of years ago. Despite the darker tone, Davies emphasized the series remains accessible to new viewers while also rewarding long-time fans with nods to the Doctor Who universe.

Filming locations in Cardiff included the Bay, Penylan, Cardiff City Hall, and National Museum Cardiff, with other Welsh locations such as Merthyr Mawr, Newport, Swansea, and Atlantic College (St Donats Castle). Mbatha-Raw described the underwater sets as “really, really epic,” noting how stepping into Salt’s domain felt like entering another world. Davies praised the design team, calling the sets “absolutely gorgeous.”

With its blend of thrilling action, environmental themes, and stunning visuals, The War Between the Land and the Sea expands the Doctor Who universe in bold new directions, proving that the franchise can captivate audiences even without the Doctor at the center.