Slow Horses Season 6 review – the best spy show, at full strength

🐴 Introduction

🐴 This review is part of our Slow Horses hub — every season reviewed and ranked, plus why the show works so well.

There is a point in every long-running series where you start to wonder whether it will ever feel this good again. Joe Country and the novel that follows it answer that question for Slow Horses with an emphatic yes. Season 6 is a perfect 5 out of 5, and I did not have to talk myself into it.

What makes that remarkable is the job it had to do. Previous seasons adapted one book each. This one folds two of Mick Herron’s Slough House novels into six episodes, which on paper is a recipe for a rushed first half and a cluttered finale. It is neither. The season moves with a confidence that suggests the writers knew exactly where every thread was going before the first episode was shot.

If you already love the show, you have probably started. If you have not, this is the season that shows what everybody has been going on about, though you should start at Season 1 rather than here.

🕵️ The setup that never gets old

The reason I love this show is the premise, and Season 6 is the best argument for it yet. Slough House is where MI5 sends the agents it cannot bring itself to sack: the ones who failed, drank, gambled, lost a file or crossed the wrong person. They are exiled to a shabby office and handed paper-pushing work, and they are expected to stay quiet and quit.

That is the setup, and it still works because the failure is genuine. These are not secretly brilliant operatives biding their time. They are people who got it wrong, who know it, and who then keep stumbling into real operations anyway. A spy thriller built on competence runs out of road; one built on failure keeps finding new ways to hurt its characters. This season finds several.

Where the spy-agency material works best is in the friction between Slough House and Regent’s Park. Diana Taverner is now settled into her new role as First Desk, and the season uses that power to put real pressure on Jackson Lamb’s team. The politics between the two buildings carry as much tension as any of the field work, and they give the season its spine: this is a fight for who survives inside the service, as much as against anyone outside it.

Without spoiling anything, this is a season in which the team is under attack more seriously than ever before, and in which the show is not afraid to follow that through. Reviewers have warned about deaths and returns, and that is fair. Do not go in assuming everybody makes it out.

📚 Two books, six episodes

The adaptation decision deserves its own section, because it is the biggest risk the show has taken. Joe Country is book six, Slough House is book seven, and the two have been combined into one run.

It works for a reason the books themselves suggest: they are two halves of the same conversation. The first pushes the characters out of their comfort zone and back toward the past. The second turns the pressure on the office itself. Written together, they feel like one escalating story rather than two stitched ones.

The cost is that the season has less room to breathe than earlier ones. Where Season 4 could spend an episode on a single conversation, Season 6 has to keep moving. For me, that was a gain. The pace never drops, and the quieter character moments that do land are all the stronger for being rationed.

One practical note for readers of the novels: folding two books into one run means the season has to compress, so do not expect every scene from the page. If you have never read them, the novels are a good way to extend the experience, and they are funnier on the page than most dramas manage to be on the screen.

🎭 Characters & performances

Jack Lowden’s River Cartwright carries a large part of this season, and his storyline is what several critics singled out as some of Lowden’s best work in the show. He has always been the closest thing Slough House has to a conventional hero, and the season uses that gently against him: River wants to be the person who gets things right, in a place that is designed to make sure he does not.

Gary Oldman’s Jackson Lamb is, as ever, the gravitational centre of the show. Six seasons in, he is still unimprovable: filthy, cruel, brilliant and unmistakably loyal underneath. The season rewards that with more to do than he has had for a while, and the dynamic with Kristin Scott Thomas’s Taverner is the best it has been. Their scenes are a duel conducted entirely in insults and silences.

The ensemble around them remains superb. Christopher Chung’s Roddy Ho, Aimee-Ffion Edwards’s Shirley Dander, Rosalind Eleazar’s Louisa Guy and Saskia Reeves’s Catherine Standish all get meaningful material, and Joanna Scanlan, Samuel West and Ruth Bradley keep the Regent’s Park politics lively. New to the cast is Lenny Rush, and reviewers have been consistent that he makes the biggest impact of the newcomers as a young person caught up in the season’s machinations.

🎬 Craft: the best-looking spy show on TV

The visuals are the other half of why this season hits so hard. The staging is simply outstanding. Adam Randall directs, and the season has a look that sets it apart from almost anything else on television: it is shot like a feature film, with a framing and a sense of scale that you rarely get from a weekly spy drama, and you notice how carefully the camera is placed in almost every scene.

What I love about it is the restraint. This is not a show that shouts about its production values. It has a confident, cinematic eye, but it uses it in service of the story, so that a long, quiet shot of a character realising something feels as deliberate as any action set piece. Season after season it looks better, and Season 6 is the best-looking yet. If you have a decent screen and a decent soundbar, it is worth using them.

The score and sound design follow the same philosophy. The title theme is still one of the best earworms in television, and the season uses silence as skilfully as it uses music.

📈 Where it sits among the seasons

The show has an unusually consistent record. For us, Season 1 is a 5, Seasons 2, 3 and 4 are 4.5, and Season 5 was a 4 as our first sign of a formula showing its seams. Season 6 returns to the top: a 5 out of 5, and in many ways the most complete season since the first.

Critics have been broadly in agreement, with Tom’s Guide giving it 4.5 out of 5 and calling it one of the best shows of 2026 so far, and Rotten Tomatoes showing a 100 per cent critic score at the time of writing. For a show in its sixth season, that is rare. Most long-running dramas are fading by now. This one has found a second gear.

👨‍👧 The dad perspective

Six episodes, roughly 45 minutes each, released weekly: it is the best use of a weeknight in streaming, and it does not ask you to give up an evening on a whim. If you have time for one episode after the kids are in bed, this is the show to spend it on.

Age guidance: 16 and up, and really an adult show. There is strong violence, very strong language in almost every scene and several dark moments. It is not one to put on with the kids around, and there is no version of it that is suitable for younger children.

Where to start: at Season 1. Our Season 5 review covers the previous run, and the reviewers who have flagged this are right: Season 6 leans on what has gone before, and the big moments land because you know these people. Our Slow Horses hub maps every season to the book it adapts, and our full ranking of the show is a good way to decide how to approach the back catalogue. Each season runs on Apple TV and a dedicated box such as an Apple TV 4K makes the whole experience smoother.

Rewatch value: very high. This is a show that gets better on the second viewing, when you can pick up the lines and glances you missed while following the plot.

✅ Pros & cons

Catching up before the next season? Prime Video’s 30-day free trial is a handy way to fill the gaps between episodes. Check the catalogue on the day rather than assuming anything specific is on it.

Is Slow Horses Season 6 worth watching?

Yes, and it is our highest rating. We give Season 6 a perfect 5 out of 5: two novels folded into six episodes without losing pace, a team under real pressure, and the best-looking season of the show so far.

Which books does Slow Horses Season 6 adapt?

Season 6 adapts two of Mick Herron’s Slough House novels, Joe Country (book six) and Slough House (book seven), in a single six-episode run.

How many episodes is Slow Horses Season 6?

Six episodes, released weekly on Apple TV from 16 September to 21 October 2026.

Do I need to watch the earlier seasons first?

Yes. Season 6 leans on events from earlier seasons, and its biggest moments land because you have spent time with these characters. Start with Season 1 and work forward.

Is Slow Horses Season 6 suitable for kids?

No. We would put it at 16 and up: there is strong violence, strong language in almost every scene and dark themes. It is written for adults.

Is there a Season 7 of Slow Horses?

Yes. Apple has renewed the show for a seventh season.