‘Slow Horses’ Confirms James Callis’ Return for Season 7, Plus Adds New Cast

“I know that Gary [Oldman] has expressed a desire to play Lamb forever and that Mick [Herron] is still writing the books, so I hope it will go for as long as people want it,” Slow Horses executive producer Will Smith told TV Insider in October 2024. Well, it certainly seems like it will keep going, with the Apple TV drama already renewed through its eighth season.

On Monday, October 19, two days ahead of the Season 6 finale, Apple TV announced the cast for the next installment and confirmed the return of James Callis, which isn’t a surprise given the book on which Season 7 is based.

Read on for everything we know about Slow Horses Season 7, from the cast to the Mick Herron book on which it will be based.

When was Slow Horses renewed for Season 7?

On July 8, 2025, Apple TV announced that the series was renewed for a six-episode Season 7.

“Slow Horses has won fans all over the world with its unique mix of self-deprecating British humor and high-octane action. I’m delighted viewers will have another season to enjoy Gary’s magnificent performance as Jackson Lamb alongside the Slow Horses slightly inept spycraft,” said Jay Hunt, creative director, Europe, Apple TV+, in a statement.

Apple TV

When does Slow Horses Season 7 premiere?

A premiere date has yet to be announced, but we wouldn’t be surprised if it’s fall 2027, given the previous seasons’ releases. Season 1 premiered in April 2022, Season 2 in December 2022, Season 3 in November 2023, Season 4 in September 2024, Season 5 in September 2025, and Season 6 in September 2026.

On which Mick Herron book will Slow Horses Season 7 be based?

The first five seasons of Slow Horses each cover a book of Herron’s series: Slow Horses, Dead Lions, Real Tigers, Spook Street, and London Rules. Season 6 is based on the sixth and seventh books, Joe Country and Slough House. Herron’s Bad Actors is being adapted for Season 7. The book’s synopsis reads as follows:

“In London’s MI5 headquarters a scandal is brewing that could disgrace the entire intelligence community. The Downing Street superforecaster—a specialist who advises the Prime Minister’s office on how policy is likely to be received by the electorate—has disappeared without a trace. Claude Whelan, who was once head of MI5, has been tasked with tracking her down. But the trail leads him straight back to Regent’s Park itself, with First Desk Diana Taverner as chief suspect. Has Taverner overplayed her hand at last? Meanwhile, her Russian counterpart, Moscow intelligence’s First Desk, has cheekily showed up in London and shaken off his escort. Are the two unfortunate events connected? Over at Slough House, where Jackson Lamb presides over some of MI5’s most embittered demoted agents, the slow horses are doing what they do best, and adding a little bit of chaos to an already unstable situation… There are bad actors everywhere, and they usually get their comeuppance before the credits roll. But politics is a dirty business, and in a world where lying, cheating and backstabbing are the norm, sometimes the good guys can find themselves outgunned.”

Season 8 is based on Clown Town. There are also novellas that could be adapted in future seasons.

“Mick has talked about doing a standalone, not from a book, so I’m sure that’s possible,” Smith told TV Insider in October 2024. He also shared that there’s quite a bit of “material in the Slough House world to be mined,” including “a couple of novels that Mick’s done that introduced characters that then come into Slough House that flesh out the backstories.”

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What will Slow Horses Season 7 be about?

In season 7, according to Apple TV, Lamb and his Slow Horses are on the hunt to find and neutralize a mole at the heart of British Government before they can bring down the state.

Who’s in the Slow Horses Season 7 cast?

We’ll have to wait to see if everyone survives the Season 6 finale to see who returns. But the Season 6 cast includes Gary Oldman (Jackson Lamb), Kristin Scott Thomas (Diana Taverner), Jack Lowden (River Cartwright), Saskia Reeves (Catherine Standish), Rosalind Eleazar (Louisa Guy), Christopher Chung as (Roddy Ho), Aimee-Ffion Edwards (Shirley Dander), Joanna Scanlan (Moira Tregorian), Samuel West (Peter Judd), Ruth Bradley (Emma Flyte), Tom Brooke (J.K. Coe), Jonathan Pryce (David Cartwright), and Hugo Weaving (Frank Harkness), with new addition Lenny Rush. Plus, Olivia Cooke returned as Sidonie “Sid” Baker.  We know Brooke won’t be back, following Coe’s death in Episode 4.

James Callis returns in Season 7 as Claude Whelan.

Joining the cast are Varada Sethu, Ethan Moorhouse, Tuppence Middleton, Merab Ninidze, and Joshua McGuire.

The series is produced for Apple TV by See-Saw Films, with Jamie Laurenson, Hakan Kousetta, Iain Canning, Emile Sherman, Dan Hassid, Helen Gregory, Mick Herron, Gail Mutrux, Douglas Urbanski, and Oldman executive producers. Season 7 is adapted for television and executive produced by Ben Vanstone, with Robert McKillop directing.