Apple TV has released the first trailer for Slow Horses season six, setting up another messy assignment for Jackson Lamb and his collection of MI5 outcasts. This time, however, Slough House appears to be fighting for its own survival.
The six-episode season will premiere globally on Apple TV on September 16, 2026, with subsequent episodes arriving weekly through October 21. Gary Oldman returns as Jackson Lamb, the abrasive and frequently underestimated intelligence veteran at the centre of the series, while Olivia Cooke makes a notable return as Sidonie “Sid” Baker.
Cooke’s comeback should be particularly interesting for long-time viewers. Sid was a major presence during the show’s first season, and bringing the character back after several years gives season six another connection to the series’ earliest days. Apple has not revealed much about the circumstances surrounding her return, leaving that particular thread for the new episodes to unravel.
Season six draws from Joe Country and Slough House, the sixth and seventh novels in Mick Herron’s Slough House series. The television adaptation has never been afraid to reshape elements of Herron’s books, so using material from two novels does not necessarily indicate exactly where the season will begin or end. It does, however, suggest the series is continuing its relatively rapid journey through the source material.
The central conflict will once again involve Diana Taverner, played by Kristin Scott Thomas. Apple says the Slow Horses will find themselves on the run after Taverner pulls them into a dangerous cycle of retaliation and revenge. That puts a different spin on the usual formula, where Lamb’s team tends to operate from the margins of MI5 while becoming inconveniently entangled in much larger intelligence operations.
Much of the established ensemble is returning, including Jack Lowden, Saskia Reeves, Christopher Chung, Aimee-Ffion Edwards, Rosalind Eleazar, Joanna Scanlan, Samuel West, Ruth Bradley, Tom Brooke, Jonathan Pryce and Hugo Weaving. Lenny Rush joins the cast for season six, although details about his character have not yet been disclosed.
Behind the camera, Gaby Chiappe has adapted the season for television and serves as co-executive producer, while Adam Randall returns as director. See-Saw Films continues to produce the series for Apple TV.
Slow Horses has become one of Apple TV’s most dependable dramas since arriving in 2022, building its reputation around a combination of espionage, institutional dysfunction and dry British humour rather than the polished spy fantasy associated with much of the genre. Its fifth season received nine Primetime Emmy nominations, including Outstanding Drama Series, with Oldman and Lowden also recognised for their performances.
That consistency may now be the bigger challenge. Six seasons is a substantial run for a modern streaming drama, particularly one arriving at such a regular pace. Slow Horses has so far avoided feeling stretched beyond its premise, helped by Herron’s extensive source material and a cast comfortable with the show’s deliberately grubby corner of British intelligence. Season six will test whether Slough House can keep that momentum going when its agents are no longer merely outsiders, but targets themselves.
