Slow Horsesis back for its fourth outing, prompting many returning viewers to wonder who is in the hit Apple TV+ show’s cast.Slow Horsesseason 4’s storywill pull its plot and characters fromSpook Street, another entry inMick Herron’sSlough Houseseries of books. So far,the unconventional British spy thriller has adapted Herron’sSlow Horses,Dead Lions, andReal Tigers, promising anotherSlow Horsesentry that differs from the books in small ways, all while capturing their spirit. The series centers onMI5’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. InSlow Horsesseason 3’s ending, Catherine Standish (Saskia Reeves), the office administrator, resigns from Slough House, while River Cartwright (Jack Lowden), a somewhat-new Slough House agent, takes the all-important “Footprint” file to his grandfather (Jonathan Pryce), a former agent. ThecontroversialSlow Horsesseason 4promises to put the Cartwrights at the center of its life-threatening conspiracy.
Gary Oldman As Jackson Lamb
Date Of Birth: July 01, 2025
Actor:Born in New Cross, London, Gary Oldman is an Academy Award, Golden Globe Award, BAFTA Award-winning actor who made his film debut inRemembrance(1982).Oldman rose to prominence in Britain during the ’80s and early ’90s for his roles inSid and NancyandRosencrantz & 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’sJFKand Count Dracula inBram Stoker’s Dracula. The acclaimed actor has also appeared inTrue Romance,The Fifth Element, theHarry Potterseries,The Dark Knight Trilogy,Darkest Hour,Mank, andTinker Tailor Soldier Spy.
Harry Potter and the Prisoner of Azkaban
Darkest Hour
Winston Churchill
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: August 08, 2025
Actor:Born in Chelmsford, Essex, England,Jack Lowden rose to prominence with his turn in the 2016 BBC miniseriesWar & Peace. After winning an Olivier Award for his role inGhosts, Lowden moved into British TV and film, eventually playing golfing legend Tommy Morris inTommy’s Honourand Morrissey in the biopicEngland Is Mine. Since then, his other big-name projects have includedDunkirk,Calibre,Mary Queen of Scots,Benediction,The Lord of the Rings: The Rings of Powerseason 2, and, of course,Slow Horses.
Tommy’s Honour
Tommy Morris
Character:After a very public misstep, River Cartwright becomesSlow Horsesseason 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: June 26, 2025
Actor:Born in Redruth, Cornwall, England, Kristin Scott Thomas is a BAFTA and Olivier Award-winning actor who made her film debut in 1986’sUnder the Cherry Moon. After winning a BAFTA Award forFour Weddings and a Funeral,the actor went on to be nominated for an Oscar forThe English Patient. Kristin Scott Thomas' other big projects includeMission: Impossible,The Horse Whisperer,Gosford Park,Only God Forgives,Fleabag, andDarkest Hour, which also starred herSlow Horsescolleague Gary Oldman.
Four Weddings and a Funeral
Fleabag
Belinda Friers
Character:Throughout the first three seasons ofSlow 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: August 21, 2025
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 filmBrazil. Since then,Pryce has appeared in big-budget films, includingEvita,Tomorrow Never Dies, andPirates of the Caribbean: The Curse of the Black Pearl, in addition to acclaimed dramas likeGlengarry Glen Rossand Martin Scorsese’s adaptation ofThe Age of Innocence. Nominated for an Oscar for his role inThe Two Popes, Pryce also had incredible turns on TV inWolf Hall,Game of Thrones, andThe Crown.
Pirates of the Caribbean: The Curse of the Black Pearl
Governor Weatherby Swann
Character:A retired MI5 officer, David is River Cartwright’s grandfather, and is set to play a key role inSlow Horsesseason 4.
Hugo Weaving As Frank Harkness
Date Of Birth: July 21, 2025
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 filmsProofandThe Adventures of Priscilla, Queen of the Desert. The actor has appeared in big-budget franchises, playing Agent Smith inThe Matrix, Red Skull in the MCU’sCaptain America: The First Avenger, and Elrond inThe Lord of the Rings.
The Matrix
Agent Smith
Character:So far, not much is known about Frank Harkness, a former CIA operative-turned-mercenary who’s set to debut inSlow Horsesseason 4.
How Accurate Is Slow Horses? 6 Things The Show Gets Wrong About MI5
Based on the Slough House novels by Mick Herron, Slow Horses isn’t a totally accurate depiction of MI5, though the spy thriller nails some details.
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 inMaster of None,Harlots, andHowards End.
Christopher Chung as Roddy Ho:Chung’s first major role was in the Australian soap operaNeighbours, thoughSlow Horsesis probably his biggest project to date.
Aimee-Ffion Edwards as Shirley Dander:Edwards is best known for her roles as Sketch inSkinsand Esme Shelby inPeaky Blinders.
Kadiff Kirwan as Marcus Longridge:The actor is best known for his performances inChewing GumandFleabag.
Joanna Scanlan as Moira Tregorian:Nominated for three BAFTA TV Awards forGetting On, Scanlan has appeared in major films likeNotes on a ScandalandBridget Jones’s Baby.
Tom Brooke as J.K. Coe:Brooke’s most well-known projects include the TV seriesSherlockandPreacher.
Saskia Reeves as Catherine Standish:An actor working in TV and film, Reeves is known for her roles inWolf Halland theDuneminiseries.
Ruth Bradley as Emma Flyte:Most well-known for her roles inPrimevalandHumans, Bradley also had a stint onTed Lasso.
James Callis as Claude Whelan:Known for playing Dr. Gaius Baltar inBattlestar Galactica, Callis also appears inBridget Jones’s Diary and voices Alucard in Netflix’sCastlevania.
Sean Gilder as “Bad” Sam Chapman:Best known for playing Paddy Maguire inShameless, Gilder has also appeared inDoctor WhoandGangs of New York.
New episodes ofSlow Horsesseason 4 will premiere on Apple TV+ every Wednesday through August 02, 2025.
Slow Horses
Slow Horses follows a dysfunctional team of MI5 agents led by the notorious Jackson Lamb. Set against the backdrop of the espionage world, the agents must navigate complex operations and defend England from sinister forces, all while dealing with internal struggles and their abrasive boss.
