The Slow Horses Cast: Where Are The Slough House Agents Now And Their Shocking New Roles

The world of British espionage has never been so gloriously grubby, and as of December 10, 2025, the latest chapter of Apple TV+'s spy thriller, Slow Horses, has captivated audiences once again. The series, based on Mick Herron’s *Slough House* novels, continues to follow a motley crew of disgraced MI5 agents—the "Slow Horses"—who have been exiled to Slough House under the brilliant but utterly repulsive leadership of Jackson Lamb. With Season 5, adapted from the novel *London Rules*, having recently premiered on September 24, 2025, the ensemble cast remains the beating heart of this critically acclaimed show, balancing high-stakes thrills with pitch-black comedy.

The latest season plunges the Slough House team into a new crisis involving a mysterious data leak, a powerful journalist, and a conspiracy that threatens to expose MI5's deepest secrets. Understanding the dynamic between the core cast members—from the Oscar-winning veteran to the rising Scottish star—is essential to appreciating the show's dark charm and its commentary on modern British intelligence. Here is the definitive, updated guide to the full cast of Slow Horses, their characters, and the exciting new projects they’ve taken on beyond Slough House.

The Core Slough House Team: Cast, Characters, and Biographies

The heart of Slow Horses lies with the agents banished to Slough House, a holding pen for MI5's failures. Their individual mistakes, combined with their unexpected competence, drive the series' central conflict.

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Gary Oldman as Jackson Lamb

• Character Role: The slovenly, flatulent, and brilliant head of Slough House. Lamb is a Cold War veteran who secretly remains one of the best operators in the intelligence community, using his repulsive exterior as a cover.
• Biography Snapshot:
  • Born: March 21, 1958 (London, England)
  • Key Roles: Winston Churchill in *Darkest Hour* (Oscar-winning performance), George Smiley in *Tinker Tailor Soldier Spy*, Sirius Black in the *Harry Potter* franchise, Commissioner Gordon in *The Dark Knight* trilogy.
  • Latest & Upcoming Projects (2025/2026): Oldman is set to star in several high-profile films, including the Italian drama *Parthenope* (2025), and is attached to projects like *The Bayou*, *Dreamland*, *Flying Horse*, and the dark comedy *Criminal Empire for Dummies*.

Jack Lowden as River Cartwright

• Character Role: A talented but disgraced MI5 agent exiled to Slough House after a high-profile training exercise failure. River is desperate to redeem himself and is the series' primary action hero. Season 4 revealed the shocking truth that mercenary Frank Harkness is his biological father.
• Biography Snapshot:
  • Born: June 2, 1990 (Chelmsford, England)
  • Key Roles: Collins in Christopher Nolan's *Dunkirk*, Lord Darnley in *Mary Queen of Scots*, Siegfried Sassoon in *Benediction*.
  • Latest & Upcoming Projects (2025/2026): Lowden recently starred in the action thriller *Tornado*, showcasing his range outside of the spy genre.

Kristin Scott Thomas as Diana Taverner (The Second Desk)

• Character Role: The formidable and ruthlessly ambitious Deputy Director-General of MI5, known as "Second Desk." Taverner is Lamb's professional nemesis and former romantic entanglement, often using the Slow Horses for her own political ends.
• Biography Snapshot:
  • Born: May 24, 1960 (Redruth, England)
  • Key Roles: *The English Patient* (Oscar-nominated), *Four Weddings and a Funeral*, *Gosford Park*, and Clementine Churchill in *Darkest Hour*.
  • Latest & Upcoming Projects (2025/2026): Scott Thomas made her impressive directorial debut with the semi-autobiographical family drama *My Mother's Wedding* in 2025.

The Complete Ensemble: Slough House Agents and MI5 Power Players

The supporting cast of Slow Horses is a masterclass in British acting talent, each bringing a distinct personality to the dysfunctional Slough House family. Their collective chemistry is a major reason for the show's success and its high topical authority in the spy thriller genre.

The Slough House Team (The Slow Horses)

• Saskia Reeves as Catherine Standish: Lamb's long-suffering administrative assistant. A recovering alcoholic, she is the moral compass of Slough House and holds a complicated history with Lamb.
• Rosalind Eleazar as Louisa Guy: A sharp, capable agent wrestling with the trauma of a past mission. Her professionalism is often tested by the chaos of Slough House.
• Christopher Chung as Roddy Ho: Slough House's resident computer genius and highly arrogant tech expert. His unparalleled hacking skills are often the team's saving grace. Season 5 introduces his new girlfriend, Tara (Hiba Bennani).
• Aimee-Ffion Edwards as Shirley Dander: Introduced in Season 2, Shirley is a scrappy, unpolished agent with a fiery temper and a history of drug use. She continues to be a key player in Season 5.
• Kadiff Kirwan as Marcus Longridge: A former MI5 agent with excellent surveillance skills. *Note: Marcus was tragically killed in the line of duty during the Season 4 finale, a shocking moment that left fans reeling.*

MI5 and Political Figures (The 'Upstairs' Players)

• Jonathan Pryce as David Cartwright: River's grandfather, a retired and legendary MI5 figure known as "The Old Man." His past actions and secrets continue to influence River's life and the operations of Slough House.
• Samuel West as Peter Judd MP: A recurring figure, Judd is a right-wing Conservative Member of Parliament whose political ambition and self-obsession often intersect with MI5's covert operations. The character is often compared to a "bogeyman" politician by the book's author, Mick Herron.
• Freddie Fox as James “Spider” Webb: A high-level MI5 officer who frequently acts as a liaison—or obstruction—between Slough House and Regent's Park (MI5 headquarters).

Season 5: New Faces and The London Rules Conspiracy

The fifth season, which premiered in the fall of 2025, sees the Slow Horses investigate a seemingly innocuous data breach that quickly escalates into a major conspiracy, based on the novel *London Rules*. The plot revolves around a powerful cabal attempting to weaponize public information, pulling the Slough House team into a digital and political minefield.

Key New Cast Members for Season 5

• Victoria Hamilton as Dodie Gimball: Hamilton, known for her roles in *The Crown* and *Cobra*, joins the cast as Dodie Gimball, a powerful and highly influential journalist. Her character is central to the data leak conspiracy and the political fallout that ensues.
• Hiba Bennani as Tara: Bennani is introduced as Tara, the new girlfriend of Roddy Ho. Her presence complicates Roddy's already eccentric life and may have unexpected ties to the central plot of the season.

The Topical Authority of Slow Horses

Slow Horses succeeds because it subverts the glamour of the spy genre, presenting a world of bureaucracy, failure, and dark humor. The show's commitment to adapting one book per season ensures a steady flow of fresh, relevant material, and the high caliber of the cast—from Oscar winners like Gary Oldman to rising stars like Jack Lowden—lends significant topical authority to the production. The show's exploration of modern themes like data privacy, political corruption, and the legacy of Cold War espionage keeps it consistently fresh and unique, making it a must-watch for fans of intelligent thrillers. The recent premiere of Season 5 has only cemented its status as one of the best British spy dramas currently on television.

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