Water crisis

Russell Tovey and Gugu Mbatha-Raw head Doctor Who spin-off series The War Between The Land And The Sea

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Doctor Who isn't on this Christmas, but the world still needs saving from alien creatures. With the Time Lord otherwise engaged, the job falls to ordinary human Barclay in new spin-off The War Between The Land And The Sea.

Russell Tovey, who previously appeared in the 2007 and 2010 festive episodes of Doctor Who, plays Barclay, a lowly member of military organisation UNIT who becomes humanity's ambassador when an ancient species rises from the sea, led by the enigmatic Salt (Gugu Mbatha-Raw).

"Barclay is a very regular guy who books taxis for very important people," says Russell, 44. "He's a drifter, he's a divorcé, he's a single parent. He's slightly numb and going through the motions. We find him at the beginning suddenly thrust into a situation he wasn't expecting, and that ricochets through the trajectory of his life."

Barclay finds himself connecting with Salt, one of the Homo Amphibia and Homo Aqua species who have lain dormant under the sea for years before being awoken by pesky humans.

Doctor Who superfans may recognise them as the watery aliens who originally appeared back in 1972, when they were known as the Sea Devils and came up against the third Doctor, played by Jon Pertwee.

"Salt is quite a fearsome character. She comes with a posse of Homo Aqua and other species from the sea, and they're incredibly intelligent," says Gugu, 42. "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."

Gugu, who also previously starred in Doctor Who back in 2007, had to spend hours in the makeup chair to transform into her amphibious character.