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Slow Horses season 7 castings revealed for Doctor Who and MobLand favourites in exclusive update

A major character from the show's past is also set to return.

Gary Oldman in Slow Horses, walking through a park and speaking on the phone.

Apple TV

Published: Monday, 19 October 2026 at 1:00 pm

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With just one episode of Slow Horses season 6 left to release on Apple TV, Radio Times can exclusively reveal a host of new cast members joining the acclaimed spy drama for its upcoming seventh season.

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Varada Sethu (Doctor Who), Ethan Moorhouse (MobLand), Tuppence Middleton (Downton Abbey: A New Era), Merab Ninidze (Homeland) and Joshua McGuire (The Gentlemen) have all officially joined the show's cast for season 7, although details of their characters are yet to be revealed.

Ninidze appeared in season 6 in a minor voice role as KGB spymaster Vassily Rasnokov, so we can assume that he will be reprising that character.

Meanwhile, it has also been confirmed that James Callis will return as Claude Whelan, the former MI5 First Desk who left his role at the end of season 5 and hasn't been seen since.

Headshots of Varada Sethu and Ethan Moorhouse put next to one another.

Varada Sethu and Ethan Moorhouse. Danny Kasirye/Ioana Wolff

News of Callis's return won't be a surprise to readers of Mick Herron's books, on which the series is based. Season 7 will adapt Herron's novel Bad Actors, in which Claude Whelan plays a central role.

The official synopsis for season 7 says that it "sees Lamb and his Slow Horses on the hunt to find and neutralise a mole at the heart of British Government before they can bring down the state".

Headshots of Tuppence Middleton, Merab Ninidze and Joshua McGuire put next to one another.

Tuppence Middleton, Merab Ninidze and Joshua McGuire. Michael Shelford/Bart Pajak/Michael Shelford

Meanwhile, the blurb of the book, Bad Actors, says: "In MI5 a scandal is brewing and there are bad actors everywhere. A key member of a Downing Street think-tank has disappeared without a trace. Claude Whelan, one-time First Desk of MI5's Regent's Park, is tasked with tracking her down.

James Callis, stood in a dark room, wearing a suit

James Callis. Apple TV+

"But the trail leads straight back to Regent's Park HQ itself, with its chief, Diana Taverner, as prime suspect. Meanwhile her Russian counterpart has unexpectedly shown up in London but has slipped under MI5's radar. Over at Slough House, the home for demoted and embittered spies, the slow horses are doing what they do best: adding a little bit of chaos to an already unstable situation.

"In a world where lying, cheating and backstabbing is the norm, bad actors are bending the rules for their own gain. If the slow horses want to change the script, they'll need to get their own act together before the final curtain."

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We already also know that Gary Oldman will be returning as Jackson Lamb in season 7, but the rest of the returning cast has yet to be unveiled - after all, it likely depends on who makes it out of the upcoming season 6 finale alive.

Thankfully, the show is continuing to be produced at a pace, with an eighth season, based on Herron's book Clown Town, already confirmed.

Slow Horses is available to stream on Apple TV. Season 6 is being released weekly, with new episodes arriving on Wednesdays. Start your seven-day Apple TV free trial.

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Authors

Black and white cut-out portrait headshot of James Hibbs, smiling against a lime green background.

James HibbsDrama Writer

James Hibbs is a Drama Writer for Radio Times, covering programmes across both streaming platforms and linear channels. He previously worked in PR, first for a B2B agency and subsequently for international TV production company Fremantle. He possesses a BA in English and Theatre Studies and an NCTJ Level 5 Diploma in Journalism.

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