The first episode of Slow Horses Season 5, titled “Bad Dates,” arrives with a mix of its celebrated core team of MI5 misfits and new faces pulled into a fresh crisis. As the Slough House agents investigate a major public security incident, familiar dynamics shift and the show’s world expands. This guide details every character who brings the high-stakes world of Apple TV+’s acclaimed spy drama to life in the season premiere.
Returning Core Cast: The Heart of Slough House
The foundation of Slow Horses remains the brilliant, flawed, and often exasperating team exiled to Slough House. Their chemistry and individual struggles continue to drive the series in its fifth season.
Sir Gary Oldman returns as Jackson Lamb, the slovenly, sharp-witted, and unapologetically rude leader of the “slow horses.” Despite his outwardly disgraceful behavior, Lamb is a tactical genius with a fierce, hidden loyalty to his team. Oldman, known for his Oscar-winning role in Darkest Hour and as Sirius Black in the Harry Potter films, embodies the character’s deceptive brilliance.
Jack Lowden continues as River Cartwright, the talented but disgraced agent desperate to prove himself and escape his banishment. In the season’s opening, River remains a skilled and reliable operative for Lamb, navigating the fallout from previous seasons. Lowden’s other notable roles include performances in Dunkirk and the series The Gold.
The core team surrounding them includes:
- Saskia Reeves as Catherine Standish, the office administrator and recovering alcoholic who serves as the team’s moral compass and institutional memory.
- Christopher Chung as Roddy Ho, the arrogant yet indispensable tech expert and hacker whose digital skills are crucial to operations.
- Aimee-Ffion Edwards as Shirley Dander, the impulsive and unpredictable field agent with a volatile temper.
- Tom Brooke as J.K. Coe, the quiet, hoodie-wearing operative from Psych Eval who suffers from PTSD and joined the team in Season 4.
MI5 Leadership and Political Players
The power struggles at MI5’s Regent’s Park headquarters and within the British government create constant pressure on Slough House. These characters represent the political battleground in which the spies operate.
Kristin Scott Thomas reprises her role as the formidable Diana Taverner. As the Deputy Director General, or “Second Desk,” she remains a masterful political operator within MI5, often finding her ambitions in conflict with both her superiors and the messy work of Slough House. Scott Thomas is renowned for films like The English Patient and Four Weddings and a Funeral.
“Nina Gold and Melissa Gethin Clark, who cast the series, are so in tune with what they’re doing because all of the characters have some kind of trait that reflects the people that are playing them,” says actor Christopher Chung.
James Callis returns as Claude Whelan, the somewhat out-of-his-depth First Desk (Director General) of MI5. Callis is widely recognized for playing Dr. Gaius Baltar in Battlestar Galactica. Jonathan Pryce also returns as David Cartwright, River’s grandfather and a retired legendary MI5 officer now living with dementia.
New Characters Joining the Fray in Season 5
Season 5 introduces several new characters who immediately become entangled in the plot, expanding the series’ scope into London’s political arena.
A significant new face is Nick Mohammed as Zafar Jaffrey, the sitting Mayor of London who is in the midst of a tough reelection campaign. Mohammed is best known for his role as Nate Shelley in the hit series Ted Lasso. His opponent in the race is Dennis Gimball, a right-wing populist played by Christopher Villiers. Gimball’s campaign is managed by his wife, Dodie Gimball, a powerful tabloid journalist portrayed by Victoria Hamilton.
Other new additions include Cherrelle Skeete as Devon Welles, the new deputy in MI5’s internal affairs “Dogs” unit. Roddy Ho’s personal life also gets a new layer with the introduction of Tara, his girlfriend played by Hiba Bennani.
Supporting Cast and Returning Faces
The ensemble is rounded out by several key supporting players whose roles have grown over the seasons.
Ruth Bradley is back as Emma Flyte, the straight-laced and efficient head of the “Dogs,” MI5’s internal security and tactical unit. She plays a central role in investigating the major incident that kicks off the season. Kadiff Kirwan returns as Marcus Longridge, the gambling-addicted sharpshooter of Slough House.
It is important to note that Rosalind Eleazar appears as Louisa Guy in Episode 1, but her role is reduced as the character steps away from field work. Samuel West also returns in his role as the pompous and manipulative Home Secretary, Peter Judd MP.
Where to Watch the Spies of Slough House
All episodes of Slow Horses, including the new fifth season, are available to stream exclusively on Apple TV+. The series is based on the Slough House novel series by Mick Herron and was adapted for television by Will Smith.
The show has been a critical success since its premiere in April 2022, earning a high score on review aggregators and multiple award nominations. Season 5 adapts Herron’s fifth novel, London Rules, and premiered on September 24, 2025.
The series has already been renewed for a sixth and seventh season, ensuring more missions for Jackson Lamb and his team of brilliant rejects.
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