Slow Horses cast and character guide: Who plays whom in Apple TV's show?

Apple TV's British spy thriller Slow Horses, based on Mick Herron's Slough House book series, debuted with Season 1 in April 2022.

The show follows administrative purgatory, Slough House, a place where rejected and misfit MI5 officers are sent after they fail a task.

The rejected officers are led by Jackson Lamb, their unkempt and abusive leader, who anticipates that the officers will leave out of frustration with their dull and monotonous lives.

However, the Slow Horses are somehow embroiled in high-stakes cases that endanger Britain.

The show is slated for a Season 5 premiere on September 24, 2025.

Here is Apple TV's crime series' complete cast and character guide.

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Slow Horses: Main cast and character guide

1) Gary Oldman as Jackson Lamb

Apple TV's Slow Horses is led by Gary Oldman as Jackson Lamb, the head of Slough House, who manages his team of misfits. While Jackson appears to be a rude and cold leader, who often shows disrespect to his team members, he is actually very loyal and will defend them to the death.

Gary Oldman is a highly accomplished actor with a decades-long career, with projects ranging from Darkest Hour, The Dark Knight Trilogy, to the Harry Potter film series.

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2) Jack Lowden as River Cartwright

River Cartwright is an MI5 officer who ends up in Slough House after a very public training error that even gets documented. While River is adamant to rise above his status as a slow horse and show his skills to his superiors, he ends up entangled in the Slough House's events.

British actor Jack Lowden is best known for his performances in Dunkirk, The Tunnel, and War & Peace.

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3) Kristin Scott Thomas as Diana Taverner

Diana Taverner is the designated second desk and the Deputy Director General of MI5 and head of operations. She deals with the slow horses and also interacts wth Jackson Lamb, but the two often end up in conflict.

British actress Kristin Scott Thomas is most famously known for her work in Four Weddings and a Funeral, Mission: Impossible, and Darkest Hour.

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4) Saskia Reeves as Catherine Standish

The alcoholic and complicated office administrator of Slough House, Catherine Standish, is the biggest pillar of Jackson's team of misfit officers. Her sense of duty and order is one of her team's biggest strengths, while she struggles to fight the demons of her past.

Saskia Reeves is famously known for Luther and Shetland.

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Supporting characters in Slow Horses

The supporting characters in Apple TV's show include:

1) Jonathan Pryce as David Cartwright: a retired senior MI5 officer and River's grandfather

2) Rosalind Eleazar as Louisa Guy: an officer in Slough House

3) Sean Gilder as "Bad" Sam Chapman: David Cartwright's bodyguard

4) Kadiff Kirwan as Marcus Longridge

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Who were the new additions in Slow Horses Season 4?

In addition to the main and supporting cast, Slow Horses Season 4 also featured many new additions to the cast, who are as follows:

1) Hugo Weaving as Frank Harkness (The Matrix, Happy Feet)

2) Tom Brooke as J.K. Coe (Sherlock, Bodyguard)

3) Ruth Bradley as Emma Flyte (Plus One)

4) James Callis as Claude Whelan (Battlestar Galactica)

5) Kiran Sonia Sawar as Giti Rahman (Murdered by My Father)

6) Anna Wilson-Jones as Isobel Cartwright (Hotel Babylon)

7) Tom Wozniczka as Patrice (Drops of God)

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