Slow Horses is a British spy thriller television series based on the Slough House novels by Mick Herron, and adapted for television by the English comedian and writer Will Smith. It follows Slough House, an MI5 unit where disgraced or failed agents are consigned, under the supervision of Jackson Lamb (Gary Oldman). It also stars Jack Lowden, Kristin Scott Thomas, Jonathan Pryce, Hugo Weaving, Saskia Reeves, Rosalind Eleazar, Christopher Chung, Aimee-Ffion Edwards, Joanna Scanlan, Tom Brooke, Lucian Msamati, and Olivia Cooke.
The series premiered on Apple TV+ on 1April 2022 to highly positive reviews. The first five series have adapted the novels Slow Horses, Dead Lions, Real Tigers, Spook Street, and London Rules, respectively. Slow Horses has been renewed for a seventh and eighth series, based on the novels Bad Actors (series 7) and Clown Town (series 8). The sixth series, based on the novels Joe Country and Slough House, premiered on 16 September 2026. All six series have received critical acclaim, with praise for the series' direction, performances, script, tonal balance, and consistency.
Premise Slough House is a banishment room for MI5 service rejects who have seriously failed a task but not badly enough to get sacked. Those consigned there are known as "slow horses", a play on the name of the place itself, Slough House, and an expression for people who are slow at thinking and action. Those assigned there are expected to endure dull, routine tasks, along with verbal abuse from their boss, Jackson Lamb, who anticipates that they will leave out of boredom or frustration. Life in Slough House is defined by drudgery, yet the Slow Horses somehow get involved in investigating cases that endanger Britain.
Cast and characters Main Gary Oldman as Jackson Lamb, the head of Slough House who is unkempt, flatulent and rude with a sour wit, all disguising a tactical sharpness and firm loyalty to his agents. Jack Lowden as River Cartwright, an up-and-coming MI5 agent abruptly shunted to Slough House after a very public training-exercise blunder. Kristin Scott Thomas as Diana Taverner, the ambitious Deputy Director General of MI5 and head of operations, designated "Second Desk" until the end of series 5 when promoted to "First Desk", Director General of MI5. Jonathan Pryce as David Cartwright (series 4–6; special guest series 1–3), River's grandfather, and a former senior MI5 official with a legendary reputation, often known as "The Old Bastard". Hugo Weaving as Frank Harkness (series 4 and 6), a former CIA operative turned ruthless mercenary and the biological father of River Cartwright. Saskia Reeves as Catherine Standish (series 5–present; co-starring series 1–4), Slough House's loyal office administrator, and a recovering alcoholic traumatised by the death of her former boss, Charles Partner. Rosalind Eleazar as Louisa Guy (series 5–present; co-starring series 1–4), assigned to Slough House after a tail operation went badly wrong. Christopher Chung as Roddy Ho (series 5–present; co-starring series 1–4), an arrogant and obnoxious computer nerd and former hacktivist with undeniable technical skills. Aimee-Ffion Edwards as Shirley Dander (series 5–present; co-starring series 2–4), a physically capable agent undone by drug and anger issues. Joanna Scanlan as Moira Tregorian (series 6; co-starring series 4), one of the Queens of the Database (record keepers), banished to Slough House by Claude Whelan. She becomes Catherine's temporary replacement. Tom Brooke as J.K. Coe (series 6; co-starring series 4–5), the newest "Slow Horse" and former operative from Psych Eval. He is reclusive and has PTSD. Lucian Msamati as Oliver Nash (series 6), the chairman of the Limitations Committee overseeing MI5's activities. Olivia Cooke as Sidonie "Sid" Baker (series 6; co-starring series 1), a competent, likable MI5 agent inexplicably assigned to Slough House.
Special guests Sophie Okonedo as Ingrid Tearney (series 1 and 3), the Director General of MI5, often referred to as "First Desk". Katherine Waterston as Alison Dunn (series 3), an MI5 agent who uncovers a dark secret at the heart of the agency. Sope Dirisu as Sean Donovan (series 3), a former head of security at the British embassy in Istanbul.
Slough House Dustin Demri-Burns as Min Harper (series 1–2), assigned after absent-mindedly leaving a top-secret disk on the train. Paul Higgins as Struan Loy (series 1 and 6), assigned after sending an inappropriate work email. Kadiff Kirwan as Marcus Longridge (series 2–4), who tends to gamble on the job.
Others Notable other characters appearing in more than one series include:
Chris Reilly as Nick Duffy (series 1–3), head of MI5's internal affairs and ruthless tactical unit nicknamed the "Dogs". Chris Coghill as Hobbs (series 1 and 3), a member of the Dogs. Samuel West as Peter Judd MP (series 1–3 and 5–6), a ruthlessly ambitious right-wing Conservative politician who is later promoted to Home Secretary. Freddie Fox as James "Spider" Webb (series 1–3), a smug MI5 agent based at Regent's Park headquarters. Naomi Wirthner as Molly Doran (series 2–present), an ill-tempered MI5 records keeper at Regent's Park. Sean Gilder as "Bad" Sam Chapman (series 2–4), former Head Dog and David Cartwright's bodyguard turned private detective, whom Lamb continues to consult. Ruth Bradley as Emma Flyte (series 4–present), the straight-minded new head of the Dogs. James Callis as Claude Whelan (series 4–5), the bumbling, over-promoted new Director General of MI5 or "First Desk".
Notable other characters appearing in Series 1 include:
Antonio Aakeel as Hassan Ahmed, Leeds University student kidnapped by the Sons of Albion, an extremist far-right group. Paul Hilton as Robert Hobden, a disgraced and struggling journalist with ties to extremist far-right groups. Sam Hazeldine as Moe / Alan Black, the leader of the subgroup of the Sons of Albion that kidnaps Hassan Ahmed, with a secret to hide. Brian Vernel as Curly, a fanatical member of the Sons of Albion. Stephen Walters as Zeppo, a member of the Sons of Albion. David Walmsley as Larry, a member of the Sons of Albion. James Faulkner as Charles Partner, the deceased former Director General of MI5 during the Cold War, whom Standish worked for as his personal assistant.
Notable other characters appearing in Series 2 include:
Rade Šerbedžija as Nikolai Katinsky, a former KGB agent living in exile in London after defecting at the end of the Cold War. Marek Vašut as Andre Chernitsky, a former KGB operative and assassin who operated during the Cold War. Alec Utgoff as Arkady Pashkin, a fixer for oligarch Ilya Nevsky. Catherine McCormack as Alex Tropper, a local resident in the small village of Upshott, the wife of Duncan and mother of Kelly. Adrian Rawlins as Duncan Tropper, a pub owner in Upshott, the husband of Alex and father of Kelly. Tamsin Topolski as Kelly Tropper, a pub barmaid in Upshott and the daughter of Alex and Duncan. Phil Davis as Richard Bough, aka Dickie Bow, a former MI5 officer, who was disgraced and is long since retired.
Notable other characters appearing in Series 3 include:
Siôn Daniel Young as Douglas, an eccentric MI5 records keeper. Charlie Rowe as Ben, a member of Donovan's team. Eliot Salt as Sarah, a member of Donovan's team. Gavin Spokes as Sly Monteith, head of the private security firm Chieftain. Nick Blood as Sturges, a Chieftain operative.
Notable other characters appearing in Series 4 include:
Kiran Sonia Sawar as Giti Rahman, an MI5 agent at Regent's Park Tom Wozniczka as Patrice, a mercenary working under Harkness Anna Wilson-Jones (voice) as Isobel Cartwright, River's mother and David's daughter.
Notable other characters appearing in Series 5 include:
Nick Mohammed as Zafar Jaffrey, the Mayor of London who is seeking reelection Hiba Bennani as Tara Younis, Roddy's apparent girlfriend Christopher Villiers as Dennis Gimball, a firebrand right-wing MP running for Mayor. Villiers previously had a cameo as a different far-right politician, Roger Simmonds, in series 1. Victoria Hamilton as Dodie Gimball, Dennis's wife and campaign manager who writes for a tabloid newspaper Cherrelle Skeete as Devon Welles, Flyte's deputy and fellow former Met officer turned Dog Monty Ben as Farouk, the leader of a Libyan terrorist cell staging attacks across London as part of a destabilisation campaign Fady Elsayed as Kamal, a member of Farouk's group Ahmed Elmusrati as Sami, a member of Farouk's group Abraham Popoola as Tyson Bowman, Jaffrey's chief of staff
Notable other actors appearing in Series 6 include:
Kyle Soller as Jim, an assassin hunting Slough House agents MyAnna Buring as Jane, an assassin hunting Slough House agents Harry Lloyd as Damien Cantor, a right-wing media mogul and news channel owner Dylan Smith as Andrew Nesmith, a former Dog with stolen critical intel Lenny Rush as Reece Nesmith, a child witness and Andrew's son Barbara Marten as Anne, an elderly lady who shelters River and Sid Zrinka Cvitešić as Natasha Carrington, Cantor's Russian handler Ben Tavassoli as Cyrus, one of Harkness' mercenaries Niall Wright as Anton, one of Harkness' mercenaries Merab Ninidze as Vassily Rasnakov, First Desk of Russia's GRU
Episodes
Series overview
Series 1 (2022) Slow Horses is based on the novel of the same name by Mick Herron, which is part of the author's Slough House series. It tells the story of a team of British intelligence agents who have all committed career-ending mistakes, and subsequently work in a dumping ground department of MI5 called Slough House.
Series 2 (2022)
Series 3 (2023)
Series 4 (2024)
Series 5 (2025)
Series 6 (2026)
Production
Development The series was given a straight to series order by Apple TV+ in October 2019, with English writer and comedian Will Smith serving as showrunner. Each of the first five series has adapted the corresponding novel in the Slough House set. In October 2024, the show was renewed for a sixth series, which jointly adapts the sixth and seventh books, Joe Country and Slough House. The fifth series premiered on 24 September 2025, followed by new episodes on a weekly basis until the season finale on 29 October 2025. In July 2025, ahead of the fifth series premiere, Apple TV+ renewed for a seventh series which is to be based on Bad Actors. The sixth series premiered on 16 September 2026, with new episodes being released on a weekly basis until the finale on 21 October 2026. The day before the sixth series premiered, Apple TV renewed the show for an eighth series, based on the novel Clown Town.
By 2025, the series began receiving praise for its production schedule, which allows it to release seasons yearly despite being a streaming series. The Wall Street Journal released an op-ed regarding the show's production schedule and strategy, which includes filming seasons back-to-back, and having multiple phases of production in motion at once.
In July 2025, it was announced that Smith would depart as showrunner after the fifth series, with Gaby Chiappe taking over as head writer for the sixth series, and Ben Vanstone for the seventh and eighth. Smith described his departure as a "practical decision" in the face of difficulties managing scriptwriting for two series at a time, per the show's established schedule of simultaneously shooting one series while writing and pre-producing the next.
Casting In October 2019, along with the series order, Gary Oldman was announced to star. The cast was rounded out in December 2020 with the additions of Olivia Cooke, Jonathan Pryce, Kristin Scott Thomas and Jack Lowden.
Filming