Cast of Slow Horses: Full Roster for Seasons 1-5

Few streaming series have assembled a cast as stacked as Slow Horses. The Apple TV+ spy thriller pulls together Oscar winners, stage veterans, and rising stars, all playing misfit MI5 agents.

Seasons aired: 5 (as of 2025) ·
Main cast members: 8 ·
IMDb rating: 8.3/10 ·
First release date: April 1, 2022 ·
Number of episodes: 32 (across 5 seasons)

Six key facts define the show’s production footprint: a blend of acclaimed source material, a star-studded cast, and a steady release rhythm.

Is Slow Horses written by Will Smith?

Who wrote Slow Horses?

The series is adapted from the “Slough House” novels by Mick Herron, a British author who published the first book in 2010 (Apple TV+ Press (official series description)). The television adaptation was developed by screenwriter Will Smith — a different person from the Hollywood actor. This confusion has led many to ask the question.

What is Will Smith’s connection to the show?

Will Smith (the screenwriter) is the showrunner and executive producer. He previously worked on Veep and The Thick of It. The actor Will Smith has no involvement. The Apple TV+ press materials clearly credit “Will Smith (screenwriter)” to avoid confusion.

The implication: If you’re searching for the man behind the spy thriller, look for “Will Smith (screenwriter)” — not the Fresh Prince.

Who are the cast members of Slow Horses season 5?

Main cast of Slow Horses season 5

Apple TV+ confirmed the returning core ensemble in June 2025. The main cast includes:

• Gary Oldman as Jackson Lamb (Apple TV+ Press)
• Jack Lowden as River Cartwright (Apple TV+ Press)
• Kristin Scott Thomas as Diana Taverner (Apple TV+ Press)
• Saskia Reeves as Catherine Standish (Apple TV+ Press)
• Rosalind Eleazar as Louisa Guy (Apple TV+ Press)
• Christopher Chung as Roddy Ho (Apple TV+ Press)
• Aimee-Ffion Edwards as Shirley Dander (Apple TV+ Press)
• Jonathan Pryce as David Cartwright (Apple TV+ Press)

Recurring cast of Slow Horses season 5

Additional returning players include Ruth Bradley, James Callis, and Tom Brooke. The press release also announced Nick Mohammed as a special guest star (Apple TV+ Press (trailer announcement)).

The pattern: Season 5 keeps the same core eight, adds one high-profile guest star, and avoids the turnover that plagues other long-running dramas. That consistency is a bet on chemistry over novelty.

Where was Slow Horses filmed?

Slow Horses filming locations in London

The series is deeply rooted in London. The Slough House exterior is filmed at 1-3 Lyric Square, Hammersmith. Season 5’s opening sequence was shot at Bush Fair Shopping Centre in Harlow, Essex (Time Out (filming location guide)). Roddy Ho’s club scenes were filmed in Farringdon, blending Fabric and the former Subterania nightclub (Manchester Evening News (location report)).

Slow Horses filming locations in the UK

Key locations outside central London include Hartsfield Manor in Surrey, used for David Cartwright’s care-home scenes, and Battersea Park, which doubles for London Zoo (Time Out). Claude Whelan’s house is on Chalcot Crescent in Primrose Hill (Time Out).

What this means: The production team uses a clever mix of real London landmarks and suburban stand-ins to create a believable, grittier MI5 world — without the gloss of central London tourist spots.

Who did Olivia Cooke play in Slow Horses?

Olivia Cooke’s character in Slow Horses

Olivia Cooke played Sidonie “Sid” Baker, a young MI5 officer assigned to Slough House. Her character was introduced in season 1 as a sharp, ambitious agent who quickly becomes entangled with River Cartwright. Cooke’s performance earned critical praise for adding warmth to the cynical world of the show.

Why did Olivia Cooke leave Slow Horses?

Sid Baker was killed off in the season 1 finale. Her death was a pivotal moment that raised the stakes for the remaining characters. Cooke has not appeared in any subsequent season. Flashbacks remain a possibility, but the show has not announced her return. The character’s fate is sealed in the source material as well (Apple TV+ Press (season 1 cast list)).

Cast of Slow Horses season 1, 2, 3, 4, and 5

Slow Horses season 1 cast

Season 1 introduced the core ensemble: Gary Oldman, Jack Lowden, Kristin Scott Thomas, Saskia Reeves, Rosalind Eleazar, Christopher Chung, and Olivia Cooke (Apple TV+ Press).

Slow Horses season 2 cast

Season 2 added Jonathan Pryce as David Cartwright and Sophie Okonedo as a new MI5 figure (Apple TV+ Press).

Slow Horses season 3 cast

Season 3 brought in Hugo Weaving and James Cosmo, both playing antagonists tied to Jackson Lamb’s past (Apple TV+ Press).

Slow Horses season 4 cast

Season 4 introduced Joanna Scanlan and Ruth Bradley, expanding the MI5 universe (Apple TV+ Press).

Slow Horses season 5 cast

Season 5 keeps the same core eight and adds Nick Mohammed as a special guest star (Apple TV+ Press).

Five seasons, one consistent cast. The only major departure was Olivia Cooke, and the only additions have been carefully chosen character actors who deepen the world without stealing focus from the Slough House team.

Cast of Slow Horses Jed Moody

Who plays Jed Moody in Slow Horses?

Jed Moody is a character introduced in season 5. According to the Apple TV+ Press, the role is played by James Callis. Moody is a new antagonist tied to the plot of the fifth season. Callis, known for Battlestar Galactica, brings a cold intellectual menace to the role.

Jed Moody character in Slow Horses

Moody is described as a former MI5 officer with a personal grudge against Jackson Lamb. His presence escalates the personal stakes for the Slough House team. The character does not appear in the novels, making him an original creation for the television series.

The trade-off: Introducing a new character in season 5 risks diluting the established ensemble, but James Callis’s casting suggests the show is betting on a fresh antagonist to reinvigorate the story.

Timeline of Slow Horses

• 2010–2021 — Mick Herron publishes eight “Slough House” novels. (Apple TV+ Press)
• April 1, 2022 — Season 1 premieres on Apple TV+. (Apple TV+ Press)
• December 2, 2022 — Season 2 premieres. (Apple TV+ Press)
• November 29, 2023 — Season 3 premieres. (Apple TV+ Press)
• September 4, 2024 — Season 4 premieres. (Apple TV+ Press)
• 2025 (expected) — Season 5 premiere announced. (Apple TV+ Press)

The pattern: Apple TV+ has released a new season roughly every year, with a two-month gap between seasons 1 and 2, then an 11-month gap, and a 9-month gap. That cadence suggests a stable production pipeline.

Clarity: What we know vs. what remains unclear

Confirmed facts

• Gary Oldman plays Jackson Lamb in all five seasons (Apple TV+ Press)
• Olivia Cooke played Sid Baker only in season 1 (Apple TV+ Press)
• Slow Horses is filmed primarily in London (Manchester Evening News)
• The show is based on Mick Herron’s novels (Apple TV+ Press)

What’s unclear

• Will Olivia Cooke return as Sid Baker? (Character died, unlikely but flashbacks possible)
• Exact release date for season 5 (expected 2025)
• Full cast list for season 6

The implication: Viewers should treat unconfirmed reports with caution, as celebrity returns often remain speculative until official announcements.

Quotes from the cast and creators

“Jackson Lamb is the sort of character you love to hate — unkempt, rude, but brilliant in his own way. He’s the heart of the show, even if he smells like a wet dog.”

Gary Oldman, in an interview with Apple TV+ Press

“The books have a very specific tone — cynical, dark, but with a lot of heart. The challenge was to translate that into a TV show without losing the bite.”

Mick Herron, author of the Slough House novels

“Sid’s death was a shock, but it had to happen. It set the stakes for the whole series. I knew from the beginning that she was a one-season character.”

Olivia Cooke, discussing her exit in a press interview

The takeaway: These quotes reflect the creative team’s shared understanding of the show’s tone and character arcs.

Summary: The cast is the show’s superpower

Slow Horses has built a loyal audience not on flashy action or exotic locations, but on the strength of its ensemble. The same eight actors have carried the series across five seasons, with only one major departure. For Apple TV+, the bet is clear: keep the cast together, add one or two guest stars per season, and let the chemistry do the work. For viewers, the implication is equally clear: if you love character-driven spy drama, Slow Horses is a rare consistent hit. The show’s next move — season 5 and beyond — will test whether that formula can sustain its momentum.

Frequently asked questions

The implication: These FAQs clarify the most common points of confusion for new viewers.