Slow Horses Season 4 Release, Cast & Everything We Know

By Klein Felt Posted:
Slow Horses Jackson Lamb

Slow Horses on Apple TV+ looks primed for a 2024 release, with its stacked cast returning to the saddle for more streaming fun. 

The British spy drama is lining up for its Season 4 debut, continuing one of the streamer's best-rated TV series. 

Led by Gary Oldman and Kristin Scott Thomas, Slow Horses tells the story of the workers within an administrative department of MI5 which is known for being the place to send the rejects of the rest of the British intelligence agency. 

When Is Slow Horses Season 4 Releasing?

Slow Horses Gary Oldman
Apple TV+

Despite being announced in June 2022 (as part of a great Slow Horses renewal), no official release timing has been made public for Slow Horses Season 4. 

The showrunner of the Apple TV+ drama, Will Smith, previously hinted the show could return before the end of the year, telling fans in December 2023 that the series would come back "this time next year" (via Decider):

“I genuinely don’t know. But I can tell you that it won’t be later than this time next year. So you won’t have to wait longer than a year.”

Filming for Season 4 began in March 2023 (per Deadline) and has seemingly wrapped as production reportedly already begun on Season 5, according to KFTV

It remains unclear when exactly Season 4 finished principal photography, but with reports from outlets like The Daily Mail revealing work is being done on Season 5, one can assume filming for the fourth season is done. 

Seasons 2 and 3 of the pencil-pushing spy thriller debuted in November/December, so there is a good chance Season 4 will follow suit and come to Apple TV+ sometime around November or December 2024. 

Who’s Cast in Slow Horses Season 4?

Much of the cast for Slow Horses Season 4 has been confirmed, with many of the show's biggest names back for more fun and a few new additions.

Having been a part of the series since the beginning, Gary Oldman will return as the curmudgeonly Jackson Lamb in Season 4. Jackson is the head of the Slough House division at the heart of Slow Horses and will continue to be a major piece on the series' chessboard moving forward. 

Joining Oldman will also be Kristin Scott Thomas as MI5 Director Diana Taverner and Jack Lowden's up-and-coming Slough House agent River Cartwright. 

The full returning cast for Slow Horses Season 4 can be seen below:

  • Gary Oldman - Jackson Lamb
  • Kristin Scott Thomas - Diana Taverner
  • Jack Lowden - River Cartwright
  • Saskia Reeves - Catherine Standish
  • Rosalind Eleazar - Louisa Guy
  • Christopher Chung - Roddy Ho
  • Freddie Fox - James “Spider” Web
  • Chris Reilly - Nick Duffy
  • Samuel West - Peter Judd
  • Sophie Okonedo - Ingrid Tearney
  • Aimee-Ffion Edwards - Shirley Dander
  • Kadiff Kirwan - Marcus Longridge
  • Jonathan Pryce - David Cartwright

A number of new actors, including Lord of the Rings actor Hugo Weaving (via Deadline), are also set to make their presence known in Season 4.

Weaving will take on the role of Frank Harkness; however, character details remain scarce. 

Other names making their Slow Horses debut in Season 4 are Ruth Bradley as Emma Flyte, James Callis as Claude Whelan, Joanna Scanlan as Moira Tregorian, and Tom Brooke as J.K. Coe.

[ Full Cast of Slow Horses Season 3 - Every Main Actor & Character In New Episodes (Photos) ]

What Will Happen in Slow Horses Season 4?

Slow Horses Season 4 will follow up on the shocking events of Season 3's finale. 

At the end of the streaming series' third season, Kristin Scott Thomas' Diana Taverner took the top job at MI5 after a controversial leak (orchestrated by the members of Slough House) ousted Sophie Okonedo's Ingrid Tearney as director of the British intelligence agency. 

It confirmed the show's fourth season will adapt Mick Herron's fourth book in the Slough House series, titled Spook Street

Spook Street's official synopsis sees the team at Slough House investigating a devastating explosion at an English shopping mall while all dealing with personal troubles at home:

"What happens when an old spook loses his mind? Does someone take care of the senile spy for good?

These are the paranoid concerns of David Cartwright, a Cold War–era operative and one-time head of MI5 who is sliding into dementia, and questions his grandson, River, must answer now that the spy who raised him has started to forget to wear pants. But River, himself an agent at Slough House, has other things to worry about. A bomb has detonated in the middle of a busy shopping center, killing forty innocent civilians—and that may only be the beginning of an escalating security situation."

According to Showrunner Will Smith, another expected plot point will be the departure of Saskia Reeves' Catherine Standish as Slough House administrator. 

Smith told Decider, "It’s very hard to imagine Slough House without Catherine," positing that Oldman's Jackson Lamb "isn’t going to function well without her:"

"In regards to the future for Lamb and Catherine, without giving too much of a spoiler, it’s very hard to imagine Slough House without Catherine. Lamb isn’t going to function well without her. Lamb needs Catherine."

He also hinted that Season 4 will be "heartfelt [and] very, very sad:"

"It goes to a very heartfelt, very, very sad place and we continue to mind that in 'Spook Street,' partly because that’s where the books go. That’s where this story goes. You know, the seeds that we’re sowing there lead directly into the events of Book 4, so there’s more of Jonathan and Jack in the next series and yeah, absolutely they reached new heights every time."

Slow Horses Seasons 1-3 are streaming now on AppleTV+.

- About The Author: Klein Felt
Klein Felt is a Senior Editor at The Direct. Joining the website back in 2020, he helped jumpstart video game content on The Direct. Klein plays a vital role as a part of the site's content team, demonstrating expertise in all things PlayStation, Marvel, and the greater entertainment industry.