MI5's Slough House — the purgatory for "slow horses" who've made career-ending missteps.

Despite being relegated to drudgery, the Slough House agents end up involved in high-profile cases — often thanks to Jackson Lamb (Gary Oldman), the rude-yet-perceptive veteran agent who heads up Slough House's team of incompetent misfits. In controversial Slow Horses season 4 promises to put the Cartwrights at the center of its life-threatening conspiracy.

Gary Oldman As Jackson Lamb

Date Of Birth: March 21, 1958

• Active Since: 1979

Actor: Born in New Cross, London, Gary Oldman is an Academy Award, Golden Globe Award, BAFTA Award-winning actor who made his film debut in Remembrance (1982). Oldman rose to prominence in Britain during the '80s and early '90s for his roles in Sid and Nancy and Rosencrantz & Guildenstern Are Dead, before becoming a member of the so-called "Brit Pack." The actor gained world-wide recognition for playing Lee Harvey Oswald in 1991's JFK and Count Dracula in Bram Stoker's Dracula. The acclaimed actor has also appeared in True Romance, The Fifth Element, the Harry Potter series, The Dark Knight Trilogy, Darkest Hour, Mank, and Tinker Tailor Soldier Spy.

Character: The slovenly and rude head of Slough House, Jackson Lamb is a veteran MI5 officer who, despite his often-awful ways, has a fierce loyalty to his "slow horses," especially River Cartwright.

Jack Lowden As River Cartwright

Date Of Birth: June 2, 1990

• Active Since: 2010

Actor: Born in Chelmsford, Essex, England, Jack Lowden rose to prominence with his turn in the 2016 BBC miniseries War & Peace. After winning an Olivier Award for his role in Ghosts, Lowden moved into British TV and film, eventually playing golfing legend Tommy Morris in Tommy's Honour ​​​​​​​and Morrissey in the biopic England Is Mine. Since then, his other big-name projects have included Dunkirk​​​​​​​, Calibre, Mary Queen of Scots, Benediction​​​​​​​, The Lord of the Rings: The Rings of Power season 2, and, of course, Slow Horses.

Character: After a very public misstep, River Cartwright becomes Slow Horses season 1's newest member of Slough House. The show's fourth season sees River, and his grandfather, pulled into the center of a life-threatening conspiracy.

Kristin Scott Thomas As Diana Taverner

Date Of Birth: May 24, 1960

• Active Since: 1984

Actor: Born in Redruth, Cornwall, England, Kristin Scott Thomas is a BAFTA and Olivier Award-winning actor who made her film debut in 1986's Under the Cherry Moon. After winning a BAFTA Award for Four Weddings and a Funeral, the actor went on to be nominated for an Oscar for The English Patient. Kristin Scott Thomas' other big projects include Mission: Impossible, The Horse Whisperer, Gosford Park, Only God Forgives, Fleabag, and Darkest Hour, which also starred her Slow Horses colleague Gary Oldman.

Character: Throughout the first three seasons of Slow Horses, Taverner is the Deputy Director General of MI5 and head of operations and designated "Second Desk," who's always eyeing the "First Desk" position.

Jonathan Pryce As David Cartwright

Date Of Birth: June 1, 1947

• Active Since: 1972

Actor: Born in Carmel, Flintshire, Wales, Sir Jonathan Pryce is a two-time Tony Award and Olivier Award-winning actor whose breakthrough screen performance came in the form of Terry Gilliam's satirical dystopian black comedy film Brazil. Since then, Pryce has appeared in big-budget films, including Evita, Tomorrow Never Dies, and Pirates of the Caribbean: The Curse of the Black Pearl, in addition to acclaimed dramas like Glengarry Glen Ross and Martin Scorsese's adaptation of The Age of Innocence. Nominated for an Oscar for his role in The Two Popes, Pryce also had incredible turns on TV in Wolf Hall, Game of Thrones, and The Crown.

Character: A retired MI5 officer, David is River Cartwright's grandfather, and is set to play a key role in Slow Horses season 4.

Hugo Weaving As Frank Harkness

Date Of Birth: April 4, 1960

• Active Since: 1981

Actor: Born in Ibadan, Nigeria to English parents, Hugo Weaving lived in Australia, South Africa, and England before his family finally settled in Sydney. Weaving's first major role came in the form of an Australian TV series, Bodyline, though he rose to prominence thanks to the Australian films Proof and The Adventures of Priscilla, Queen of the Desert. The actor has appeared in big-budget franchises, playing Agent Smith in The Matrix, Red Skull in the MCU's Captain America: The First Avenger, and Elrond in The Lord of the Rings.

Character: So far, not much is known about Frank Harkness, a former CIA operative-turned-mercenary who's set to debut in Slow Horses season 4.

Other Characters In Slow Horses Season 4

Apple TV+'s Unconventional Spy Thriller Boasts A Solid Ensemble Cast

Rosalind Eleazar as Louisa Guy: A theater actor who's moved to screen, Eleazar is known for her roles in Master of None​​​​​​​, Harlots, and Howards End.

Christopher Chung as Roddy Ho: Chung's first major role was in the Australian soap opera Neighbours, though Slow Horses is probably his biggest project to date.

Aimee-Ffion Edwards as Shirley Dander: Edwards is best known for her roles as Sketch in Skins and Esme Shelby in Peaky Blinders.

Kadiff Kirwan as Marcus Longridge: The actor is best known for his performances in Chewing Gum and Fleabag.

Joanna Scanlan as Moira Tregorian: Nominated for three BAFTA TV Awards for Getting On, Scanlan has appeared in major films like Notes on a Scandal and Bridget Jones's Baby.

Tom Brooke as J.K. Coe: Brooke's most well-known projects include the TV series Sherlock and Preacher.

Saskia Reeves as Catherine Standish: An actor working in TV and film, Reeves is known for her roles in Wolf Hall and the Dune miniseries.

Ruth Bradley as Emma Flyte: Most well-known for her roles in Primeval and Humans, Bradley also had a stint on Ted Lasso.

James Callis as Claude Whelan: Known for playing Dr. Gaius Baltar in Battlestar Galactica, Callis also appears in Bridget Jones's Diary​​​​​​​ and voices Alucard in Netflix's Castlevania.

Sean Gilder as "Bad" Sam Chapman: Best known for playing Paddy Maguire in Shameless, Gilder has also appeared in Doctor Who and Gangs of New York.

New episodes of Slow Horses season 4 will premiere on Apple TV+ every Wednesday through October 2, 2024.