'Slow Horses' Season 5 Sets a Track for September Arrival

Fans of Apple TV+'s Slow Horses, based on the Mick Herron thrillers The Slough House Series, prepare to ride out in the fall. The series, which has slowly built itself into one of Apple TV+'s most reliable and solid performers over four seasons, has set a return date for Season 5. It's perhaps the most telling release date from the streaming service, which has been working overtime in 2025 to build viewership after languishing behind the competition to the point that even FAST streamer Tubi was outperforming it. 

Season 1 was given an Emmy Award season berth in April; Seasons 2 and 3 were moved to the December holidays for a better chance at the Golden Globes and SAG Awards. Season 4 was moved to the first week of September, a surprising choice, considering most streaming services routinely flaunt how little they rely on the traditional TV season. However, for Season 5, Apple TV+ is going ultra-conventional, with a premiere in the third week of September, a spot that only old-school broadcast shows like Grey's Anatomy still honor.

Season 5 will cover the events from Herron's fifth book, London Rules. This will be the last season to be drawn from a single book, at least for now, as Season 6 will combine the next two of the nine-book series, Joe Country and Slough House. Whether or not that's a sign Apple TV+ plans to wrap up the series with Season 7 remains to be seen, but only two books will remain unadapted by the end of 2026, 2022’s Bad Actors and the forthcoming Clown Town, which will land on bookshelves on September 9, 2025, two weeks before the Season 5 premiere. (Seasons 1 through 4 covered Slow Horses, Dead Lions, Real Tigers, and Spook Street.)

Here's the Season 5 synopsis:

Slow Horses is a darkly humorous espionage drama that follows a dysfunctional team of British intelligence agents who serve in a dumping ground department of MI5 known un-affectionately as Slough House, run by Jackson Lamb, the brilliant but cantankerous leader of the spies who end up in Slough House due to their career-ending mistakes and who frequently find themselves blundering around the smoke and mirrors of the espionage world. 

In Season 5, everyone is suspicious when resident tech nerd Roddy Ho has a glamorous new girlfriend. When a series of increasingly bizarre events occur across the city, it falls to the Slow Horses to work out how everything is connected. After all, Lamb knows that in the world of espionage, the London Rules — cover your back — always apply.

Gary Oldman (Oppenheimer) once again stars as Jackson Lamb, with Jack Lowden (The Gold) as River Cartwright. The rest of the returning ensemble includes Kristen Scott Thomas (Gosford Park) as Diana Taverner, Saskia Reeves (Roadkill) as Catherine Standish, Rosalind Eleazar (The Personal History of David Copperfield) as Louisa Guy, Christopher Chung (Waterloo Road) as Roddy Ho, Aimee-Ffion Edwards (Wolf Hall) as Shirley Dander, and Jonathan Pryce (The Crown) as David Cartwright. 

Season 4 additions also returning for Season 5: Joanna Scanlan (The Larkins) as Moira Tregorian, Ruth Bradley (Guilt) as Emma Flyte, and Tom Brooke (Bodyguard) as J.K. Coe. Season 5's big new addition is Nick Mohammed (Ted Lasso) in a guest star turn. He is not listed to return fr Season 6. However! Season 6 will reportedly introduce Lenny Rush (Doctor Who) to the series... At least according to his Am I Being Unreasonable? co-stars. (Apple TV+ has not confirmed.)

Slow Horses' longtime lead writer, Will Smith, is adapting Season 5 for television. This will be his last turn in the lead writer chair, which will pass to Gaby Chiappe in Season 6. Season 3 director  Saul Metzstein returns to helm all episodes of Season 5. Smith, Metzstein, and Oldman are listed as executive producers, alongside Jamie Laurenson, Hakan Kousetta, Julian Stevens, Iain Canning, Emile Sherman, Gail Mutrux, Douglas Urbanski, and Graham Yost.

Slow Horses Season 5 is set to debut on Wednesday, September 24, 2025, with the first two episodes, followed by one episode per week through October. Season 6 is expected to follow in 2026. Seasons 1 through 4 are streaming on Apple TV+.