Slow Horses adds five actors for season seven as season six wraps on Apple TV

Season six of Slow Horses was scheduled to end on Wednesday, October 21, with its sixth and final weekly episode on Apple TV. The first cast news for season seven arrived two days before that.

Five actors are joining Gary Oldman's Jackson Lamb and his team of MI5 rejects, TVLine reported on October 19: Varada Sethu, Ethan Moorhouse, Tuppence Middleton, Merab Ninidze and Joshua McGuire. James Callis is coming back as Claude Whelan. Character details for the newcomers have not been disclosed.

For anyone who has not started the show: Slough House is the MI5 department where intelligence officers are sent after career-ending mistakes, a dumping ground the service would rather forget about. Oldman's Lamb runs it, brilliant and cantankerous, and his agents keep stumbling into operations far bigger than the paperwork they were exiled to do. The series is based on Mick Herron's novels, which won the Crime Writers' Association's Gold Dagger.

Who the five are

Here is where viewers will have seen them:

• Varada Sethu, from Andor
• Ethan Moorhouse, from MobLand
• Tuppence Middleton, from Death by Lightning
• Merab Ninidze, from Homeland
• Joshua McGuire, from The Gold

Ninidze in particular comes with spy-drama mileage. The others arrive from a Star Wars series, a crime saga, a historical drama and a heist story, which is roughly the range of trouble Slough House tends to attract.

Season seven is the mole hunt from Bad Actors

Apple set out the plan for season seven back on July 8, 2025, when it renewed the series before season five had even premiered. The new season adapts Bad Actors, from Mick Herron's Slough House novels, and runs six episodes. Apple's one-line summary: 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."

TVLine's report names Callis as the one returning actor so far. Whether anyone else from earlier seasons comes back, and which roles the five newcomers play, has not been announced.

The show is now moving faster than the books

The more interesting number is how quickly Slow Horses is eating its source material. Season six, according to Apple's June press release, adapted two novels at once: Joe Country and Slough House, the sixth and seventh books in the series, in six episodes.

Season seven moves on to Bad Actors, the next book in the series, and the gap between page and screen keeps shrinking. Apple has released seasons at a steady clip: season five premiered on September 24, 2025, and season six on September 16, 2026, with one episode a week through October 21.

Season six put the team on the run, with Kristin Scott Thomas's Diana Taverner, in Apple's words, embroiling them all "in a fatally high-stakes game of retaliation and revenge." The cast that carried it included Jack Lowden, Saskia Reeves, Christopher Chung, Aimee-Ffion Edwards, Rosalind Eleazar, Joanna Scanlan, Samuel West, Ruth Bradley, Tom Brooke, Jonathan Pryce and Hugo Weaving, with BAFTA winner Lenny Rush as the season's new addition.

Why Apple keeps ordering more

The renewal announcement gave the reasons in numbers. Season three earned nine Primetime Emmy nominations and won for Outstanding Writing for a Drama Series. Every season up to that point had a Certified Fresh score on Rotten Tomatoes, two of them at a perfect 100 percent, and season four was named the site's number one series of 2024. Oldman himself has been nominated for the Golden Globe, the Emmy and the BAFTA for playing Lamb.

Apple also renews the show far in advance. The calendar of the last two years shows how far ahead it plans:

• 2024: season six is announced.
• July 8, 2025: season seven is ordered, two and a half months before season five premieres.
• September 24, 2025: season five premieres.
• June 11, 2026: first look at season six.
• September 16 to October 21, 2026: season six airs weekly.
• October 19, 2026: first season seven casting is reported.

The series is produced by See-Saw Films, with Oldman among the executive producers. Season six was adapted for television by co-executive producer Gaby Chiappe, with Adam Randall returning as director, and both are names to watch for when Apple confirms the season seven team.

Apple has not yet given season seven a premiere date or released first-look images. Seasons one through six are on Apple TV, and with the season six finale scheduled for October 21, the wait for season seven has officially started.