As the Doctor continues his endless journey across all of time and space, his allies on Earth will soon have a war to deal with. During the Doctor Who panel at Hall H of San Diego Comic-Con on Friday, showrunner Russell T. Davies announced an upcoming five-part spinoff series, titled The War Between the Land and the Sea.

“We have got a new spinoff coming from the Whoniverse about what happens when the Doctor’s not in town,” Davies said on stage. “How does the world cope?”

The Sea Devils, an old Doctor Who enemy from the ‘70s, will feature heavily in the series. When this water-dwelling species wake up again and see what has become of Earth’s oceans in 2024, they decide to declare “war, on an epic scale” against humanity for their crimes against nature.

With the Doctor unavailable, it falls to UNIT to deal with the conflict. Jemma Redgrave will reprise her role from the most recent season as UNIT leader Kate Lethbridge-Stewart, and Alexander Devrient will be back as Colonel Ibrahim.

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But the series will be led by two new cast members, Russell Tovey and Gugu Mbatha-Raw. Both have appeared in Doctor Who before, but will now be playing new characters.

"This is not Midshipman Frame teaming up with Tish Jones — which, I would write actually,” Davies joked.

The series will be directed by Dylan Holmes-Williams, who oversaw two of the most interesting episodes from last season: “73 Yards” and “Dot and Bubble.” The latter episode, a Black Mirror riff that ended with Ncuti Gatwa’s Fifteenth Doctor being discriminated against by people he was trying to save, actually came up during the audience Q&A segment of the panel. A fan asked Gatwa about filming his tearful scene at the end of the episode.

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“The Doctor’s never been Black before, so he’s gonna be so confused by this experience,” Gatwa said. “It was really about tapping into that."

The War Between the Land and the Sea starts filming later this year, but this year’s Doctor Who Christmas special is already prepared. They played an exclusive teaser to the panel audience, teasing Bridgerton star Nicola Coughlan’s guest appearance.