Slow Horses Review: The Best Spy Show on Television Keeps Raising Its Own Ceiling

Slow Horses is the spy show that wins by lowering expectations and then exceeding them every season. Mick Herron's Slough House novels become Apple TV+ series about MI5's failure pile, the disgraced agents parked in a shabby office under Jackson Lamb (Gary Oldman), a rude, flatulent, brilliant spymaster who treats his team like inventory. Rotten Tomatoes has the series at 98% across 243 reviews, and season 6, which finished its weekly run on October 21, 2026, arrived at 100% and set an all-time RT audience score record along the way. This is currently the most reliable hour of espionage on television.

Spoiler-free verdict: Start at season 1 immediately. Slow Horses refreshes the genre by letting its spies be bumbling, and Oldman turns contempt into tradecraft. Six seasons deep, it has not missed.

What Slow Horses is about

The setup is a demotion with teeth. River Cartwright (Jack Lowden) blows a training exercise and lands in Slough House, MI5's bureaucratic exile, run by Jackson Lamb under the nominal authority of Diana Taverner (Kristin Scott Thomas) at Thames House. The conceit: Lamb's losers keep stumbling into real operations, and Lamb, who used to run the serious stuff, keeps solving them while insulting everyone in range.

Each season adapts one or more of Herron's novels. The sixth run drew from Joe Country and Slough House, the sixth and seventh books, and assembled every washed-out agent Lamb has ever collected, with Hugo Weaving joining the cast. New episodes have aired every week since April 2022, with season 6 wrapping on October 21, 2026.

Cast and performances

Oldman is the headline and the review. Shubhra Gupta at The Indian Express, scoring the season 4 premiere, described "an Oldman performance so abrasive that only he gets away with it," and The Spuel's Tim Stevens put it more simply: "Some actors exude the art from their pores. Oldman is one of them." He plays Lamb as a slob who is three moves ahead of everyone, and the show is smart enough to keep the intelligence visible under the grime. Around him: Jack Lowden's River as the field asset who keeps choosing the job, Kristin Scott Thomas' Taverner as the politician-spy, and Saskia Reeves' Catherine Standish as the show's best quiet scene partner.

What works

The tone, and it never slips. Slow Horses is funny, mean, and tense in the same scene, and director James Hawes and the writing room keep the balance across six seasons. The violence arrives abruptly and stays ugly, the London is wet and bureaucratic rather than glamorous, and the stakes are personal rather than apocalyptic. That Shelf's Pat Mullen called season 6 "a clever adaptation that produces a crisp, clean story, weaving heart-stopping action," and Firstpost's Pradeep Menon wrote in 2023 that you would have to go back to le Carré's The Night Manager to find a British spy series this tightly ratcheted. The RT critics consensus for season 1 still stands as the best description of the trick: the show "refreshes the espionage genre by letting its band of snoops be bumbling, with Gary Oldman giving a masterclass in frumpy authority."

What doesn't

Very little, at this point. Season 5 drew the lowest marks of the run, with critics calling it a stumble that remained good rather than great, and the season 6 correction was immediate. The one real cost is rhythm: weekly episodes demand patience in a streaming era built for binges, and the ensemble rotates often enough that late-season arrivals get thin coverage. A viewer who bounces off Lamb's manners in the pilot will not make it to the material underneath, which is the show's only genuine trap.

What audiences say

The audience verdict is historic. Season 6 set a new all-time Rotten Tomatoes audience score record for the platform, per ScreenRant's reporting, and the show's overall audience figure sits at 87% with an 8.3/10 critics average. RT verified audience reviews run to five-star praise with the recurring note that the show improves weekly, and the waiting-between-episodes complaints are the angriest posts the fan boards produce. TMDB has it at 8.1 from 1,071 votes, checked October 24, 2026.

Where to watch Slow Horses

All six seasons stream on Apple TV in the US, with the Apple TV Amazon Channel as an alternative, checked on October 24, 2026. Season 7 has not been announced. The series page with episode guides sits at Slow Horses streaming options and member reviews. If Lamb's old-school tradecraft is the draw, The Night Manager is the glossy counterpart, and The Americans is the long-game comparison.

Verdict

Is Slow Horses worth watching? It is the best spy show currently running, and six seasons at 98% on Rotten Tomatoes is the evidence. The show respects its audience by being small: no world-ending plot, no glamour, just a dirty office full of damaged people who keep getting it right. Start at season 1, keep Oldman's Lamb away from your drinks.

Rating: 8.7/10 (IMDb 8.3/10, Rotten Tomatoes 98% series-wide, TMDB 8.1/10; evidence-weighted, checked October 24, 2026)