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

Academy Award-winning actor Gary Oldman leads the cast of Slow Horses Season 3 as it begins to stream on Apple TV+.

Slow Horses, a highly praised spy thriller series based on Mick Herron's Slough House novels, debuted on Apple TV+ in April 2022. 

The show received the green light for a third and fourth series in June 2022 and premiered Season 3 on Wednesday, November 29, 2023. 

Set in the administrative purgatory of Slough House, the series follows Security Service (MI5) rejects, termed "slow horses," as they endure tasks and abuse under their boss Jackson Lamb (Gary Oldman).

In Season 3, the team must unite to rescue a kidnapped member from a rogue agent.

Every Main Actor & Character in Slow Horses Season 3

Gary Oldman - Jackson Lamb

Jackson Lamb, the leader of Slough House, is often unkempt, mean, and seemingly drunk. However, beneath his gritty exterior, he possesses a cunning intellect, maintaining the skills of a seasoned intelligence officer.

Gary Oldman portrays Lamb, who is known for a variety of roles in films including the Harry Potter series, The Dark Knight trilogy, and Dawn of the Planet of the Apes. He received an Academy Award for Best Actor for his portrayal of Winston Churchill in Darkest Hour and earned nominations for his roles in Tinker Tailor Soldier Spy and Mank.

Kristin Scott Thomas - Diana Taverner

In Slow Horses, Diana Taverner serves as the deputy director-general of MI5, overseeing operations and holding the position of "Second Desk."

Kristin Scott Thomas is best known for winning the BAFTA Award for Four Weddings and a Funeral and earning an Academy Award nomination for her role in The English Patient. Her filmography includes notable performances in The Seagull, Gosford Park, I've Loved You So Long, and Darkest Hour.

Jack Lowden - River Cartwright

River Cartwright is a promising MI5 agent who has been reassigned to Slough House following an attention-grabbing error during a training exercise.

Taking on the role of Cartwright again in Season 3 is Jack Lowden. The Scottish actor gained international acclaim for his role in the 2016 BBC miniseries War & Peace. 

He won an Olivier Award and the Ian Charleson Award for his performance in the adaptation of Ibsen's Ghosts and received the British Academy Scotland Award for his role in the Scottish Highlands thriller, Calibre.

Saskia Reeves - Catherine Standish

Catherine Standish, Jackson Lamb's loyal secretary at Slough House, handles clerical tasks despite their strained relationship, which oddly includes a form of affection.

Actress Saskia Reeves has had notable roles in TV series such as Spooks, The Commander, and Luther, along with significant stage performances.

Rosalind Eleazar - Louisa Guy

Louisa Guy is in the group of MI5 agents relegated to Slough House after various setbacks. Louisa plays a pivotal role in missions, facing challenges within the team and forming unexpected alliances.

Rosalind Eleazar takes on the role and is best known for her versatile performances in various TV series, including BBC's Rellik, Howards End, and ITV's Deep Water.

Christopher Chung - Roddy Ho

Roddy Ho is a computer expert with a history as a hacktivist, known for his disruptive activities in the realm of hacking and activism for various causes.

Taking on this character is Christopher Chung, who is best known for this role on Slow Horses. In addition, he is featured in the TV series Waterloo Road and Neighbours.

Freddie Fox - James “Spider” Webb

James "Spider" Webb is an operative of MI5 stationed at the headquarters in Regent's Park.

Freddie Fox is best known for his screen performances in BBC's Boy George biopic Worried About the Boy, Freddie Baxter in the series Cucumber and Banana, and Jeremy Bamber in White House Farm.

Chris Reilly - Nick Duffy

Nick Duffy is the leader of MI5's internal affairs and the tactical unit known as "The Dogs."

Taking on the role is Chris Reilly, seen also in Wrath of Man, The Head, Industry, and Cash Truck.

Samuel West - Peter Judd

Peter Judd initially portrayed a right-wing Conservative politician in the first season and then assumed the role of Secretary of State for the Home Department in Season 2.

Dominic West is best known for his roles in films such as Howards End, Notting Hill, Iris, Van Helsing, and Darkest Hour. On television, he has appeared in long-running series like Midsomer Murders and Waking the Dead and portrayed Anthony Blunt in Cambridge Spies and The Crown.

Sophie Okonedo - Ingrid Tearney

Ingrid Tearney served as the Director-General of MI5 (First Desk) in the first season and is anticipated to make a return in the upcoming Season 3.

Sophie Okonedo is renowned for her roles in Hotel Rwanda, Tsunami: The Aftermath, The Secret Life of Bees, and the BBC's The Hollow Crown. She also has a Tony Award-winning performance in A Raisin in the Sun.

Aimee-Ffion Edwards - Shirley Dander

Aimee-Ffion Edwards portrays Shirley Dander in Slow Horses, a new addition in Season 2 to the team who showcases her professionalism. 

In a pivotal moment, Jackson Lamb selects Shirley over River for a job, causing tension between River and Lamb. Edwards is best known for her roles in Skins, Peaky Blinders, and Detectorists.

Kadiff Kirwan - Marcus Longridge

Marcus Longridge did not appear in the first season of the show, but he is expected to make a return in the upcoming third season. In Season 2, his character is portrayed as having gambling issues.

Kadiff Kirwan is best known for his roles in the BAFTA award-winning show, Chewing Gum and in the Netflix series, Black Mirror. He's also seen in Strike, Timewasters, Crims, and Call the Midwife.

Jonathan Pryce - David Cartwright

David Cartwright is the grandfather of River Cartwright, having served as a retired MI5 officer with a wealth of experience and knowledge in the intelligence field.

Jonathan Pryce is best known for his Tony Award-winning performances in Comedians and Miss Saigon on Broadway and his portrayals in films such as Evita, The Age of Innocence, and The Two Popes.

Additionally, he gained recognition for his TV roles in Game of Thrones, Wolf Hall, and The Crown.

Ṣọpẹ Dìrísù - Sean Donovan

Ṣọpẹ Dìrísù, known for his role in Gangs of London, is joining Season 3 of Slow Horses as Sean Donovan, the former head of security at the British embassy in Istanbul.

Dìrísù is recognized for his roles in projects such as The Mill, Utopia, Humans, The Casual Vacancy, Siblings, Undercover, Criminal, The Huntsman: Winter's War, Sand Castle, and one Black Mirror episode.

Katherine Waterston - Alison Dunn

Katherine Waterston joins in Season 3 as Alison Dunn, an MI5 agent unraveling a concealed truth within the agency.

Katherine Waterston is best known for her roles in Inherent Vice, Steve Jobs, Fantastic Beasts and Where to Find Them and its sequels, Alien: Covenant, and The World to Come.

Slow Horses Seasons 1 and 2, as well as the first episode of Season 3, are streaming now on Apple TV+.