Full Cast of Slow Horses Season 4 - Every Main Character & Actor Who Appears (Photos)

Apple TV+'s Slow Horses is back with Season 4, and here is an extensive list of the characters and actors along for the ride.

The show follows the Slough House division of MI5, where the agency's biggest outcasts and so-called failures end up. While they may be cast aside, the group is still heavily involved in completing critical missions and saving lives.

The first episode of Season 4 aired on September 4. The rest of the episodes will air weekly, culminating in the finale on October 9.

Cast & Actors in Slow Horses Season 4

Gary Oldman - Jackson Lamb

Gary Oldman's Jackson Lamb is the leader of Slough House and the operatives it houses.

On the surface, Jackson comes off as dirty, unkept, and constantly drunk. While he's still overall a mess, he's a skilled secret agent for a reason, being both incredibly smart and capable.

Oldman has had several iconic movie roles, including Officer Gordan in The Dark Knight, George Smiley in Tinker Tailor Soldier Spy, and Sirus Black in the Harry Potter franchise.

• Instagram: @giseleschmidtofficial
• Wikipedia: Gary Oldman
• IMDb: Gary Oldman

Jack Lowden - River Cartwright

Jack Lowden's River Cartwright is one of the many outcasts of the Slough House, someone who feels he has something to prove after messing up in a training exercise.

His relationship with his grandfather, David Cartwright (Jonathan Pryce), takes center stage in Season 4, as his family's history in the agency haunts them.

Lowden has roles in Dunkirk, The Gold, The Long Song, and more.

• Instagram: @jack.lowden
• Wikipedia: Jack Lowden
• IMDb: Jack Lowden

Kristin Scott Thomas - Diana Taverner

Diana Taverner (Kristin Scott Thomas) returns for Season 4 as the MI5 Deputy Director-General and Head of Operations.

She often uses Slough House as a tool to further her career.

Thomas also delivers notable performances in The English Patient, Only God Forgives, Four Weddings and a Funeral.

• Instagram: @kristinscottthomas
• Wikipedia: Kristin Scott Thomas
• IMDb: Kristin Scott Thomas

Jonathan Pryce - David Cartwright

Jonathan Pryce plays David Cartwright, River's grandfather. He is a retired senior MI5 officer, though his path still often crosses with those at Slough House.

Pryce played Prince Philip, Duke of Edinburgh, in The Crown and Mike Evans in 3 Body Problem.

• Wikipedia: Jonathan Pryce
• IMDb: Jonathan Pryce

Saskia Reeves - Catherine Standish

After barely skirting treason charges, Saskia Reeves' Catherine Standish is assigned to Slough House.

While she's quick-witted and highly skilled like everyone else on the team, Saskia is a bit of an alcoholic.

Reeves previously played DSU Rose Teller in the fan-favorite series Luther and even appeared in three episodes of the 2000 Dune television series.

• Wikipedia: Saskia Reeves
• IMDb: Saskia Reeves

Rosalind Eleazar - Louisa Guy

Rosalind Eleazar's Louisa Guy is another of Slough House's rejected recruits. She fell into their lap after a tailing operation she led ended poorly.

Some of Eleazar's previous works include Harlots, Deep Water, Class of '09, and more.

• Instagram: @rosalind.eleazar
• Wikipedia: Rosalind Eleazar
• IMDb: Rosalind Eleazar

Aimee-Ffion Edwards - Shirley Dander

While Shirley Dander's Aimee-Ffion Edwards was an MI5 agent, she was pushed into Slough House thanks to punching her superior officer. She also happens to be a cocaine addict, so that didn't help things either. Thankfully, she's worked to clean things up a little.

Many fans will likely recognize Edwards from her time as Esme Shelby on Peaky Blinders.

• Wikipedia: Aimee-Ffion Edwards
• IMDb: Aimee-Ffion Edwards

Christopher Chung - Roddy Ho

Christopher Chung plays Roddy Ho, a former "hacktivist" who is now a tech specialist for Slough House.

Reportedly, Roddy Ho was fired by MI5 for his IT skills being "too good."

Chung can previously be seen in Waterloo Road and offers his voice talents to the PlayStation video game Horizon Forbidden West.

• Instagram: @chrispchung
• Wikipedia: Christopher Chung
• IMDb: Christopher Chung

Kadiff Kirwan - Marcus Longridge

Kadiff Kirwan’s Marcus Longridge is held down by a crippling gambling addiction that destroyed both his career and marriage. Despite that, he’s still an invaluable member of the Slough House.

Kirwan can also be seen in This Is Going to Hurt, This Way Up, and Dodo.

• Instagram: @kadiffkirwan
• Wikipedia: Kadiff Kirwan
• IMDb: Kadiff Kirwan

Joanna Scanlan - Moira Tregorian

Joanna Scanlan's Moira Tregorian has a fun nickname, Queen of the Database, and has been banished to Slough House.

Some of Scanlan's previous works include The Larkins, Boat Story, and Wicked Little Letters.

• Wikipedia: Joanna Scanlan
• IMDb: Joanna Scanlan

Tom Brooke - J.K. Coe

A man of few words, Tom Brooke's J.K. Coe is a fellow agent who joins the fun in Slow Horses Season 4. Before joining the Slough House crew, he was a former operative from Psych Eval.

Brooke played Fiore in Preacher, Bill Wiggins in Sherlock, and Andy Apsted in Bodyguard.

• Wikipedia: Tom Brooke
• IMDb: Tom Brooke

Hugo Weaving - Frank Harkness

Iconic actor Hugo Weaving joins Slow Horses as Frank Harkness, a former CIA operative who now operates as a mercenary. He will be Season 4's antagonist.

Many will know Weaving from his performance as Elrond in The Lord of the Rings series. He has also appeared in The Royal Hotel, Love Me, Expired, and more.

• Wikipedia: Hugo Weaving
• IMDb: Hugo Weaving

Ruth Bradley - Emma Flyte

MI5 has a new head of security, and the honor goes to Ruth Bradley's Emma Flyte.

Audiences can also see Flyte's performance in projects such as Ted Lasso, Guilt, and The Gold.

• Instagram: @ruthbradley24
• Wikipedia: Emma Flyte
• IMDb: Emma Flyte

James Callis - Claude Whelan

James Callis' Claude Whelan is another new addition to Slow Horses Season 4.

Claude is the recently promoted Director General of MI5 but may be out of his depth.

Callis is best known for his role as Dr. Gaius Baltar on Battlestar Galactica. His other works include Castlevania, Star Trek: Picard, and Blood & Treasure.

• Instagram: @james_callis
• Wikipedia: James Callis
• IMDb: James Callis

Sean Gilder - "Bad" Sam Chapman

In Season 4, it's revealed that Sean Glider's "Bad" Sam Chapman used to bodyguard Jonathan Pryce's David Cartwright.

Sam worked for MI5 and has since become a private intelligence contractor.

Glider recently starred in the horror film Starve Acre and has also appeared in Shadow and Bone, The Gold, and Sherwood.

• Wikipedia: Sean Gilder
• IMDb: Sean Glider

Leroy Kincaide - Bread Dog

Leroy Kincaide will play a Bread Dog in Slow Horses Season 4.

Kincaide has minor roles in Black Mirror, Gangs of London, Tom Clancy's Jack Ryan, and more.

• Instagram: @leroykincaide
• IMDb: Leroy Kincaide

Slow Horses is streaming on Apple TV+.