Slow Horses Season 6 Review: More Action, Less Intrigue

Official promotional image for Slow Horses Season 6. Apple TV promotional material, used for review and commentary.

By its third episode, Slow Horses Season 6 has its agents running for their lives, and they barely stop until the finale. Yet watching the episodes week by week, I found myself increasingly impatient. The series was never short of danger; what it lacked was the steady accumulation of discoveries that made its earlier conspiracies so absorbing.

The change in viewing habits may have contributed to that impression. Most previous seasons passed quickly when watched over a few evenings, while the weekly release exposed the structure of individual episodes. But I suspect the difference runs deeper. The sixth season places more emphasis on immediate danger than on the political and institutional manoeuvring that once made Slow Horses distinctive.

The story begins with the deaths of people connected to Slough House, MI5's dumping ground for agents whose careers have gone wrong. Jackson Lamb, played by Gary Oldman, begins investigating what appears to be a systematic campaign against former and current members of his team. As the surviving agents scatter, River Cartwright (Jack Lowden) becomes entangled in another confrontation involving his father, Frank Harkness, while Diana Taverner (Kristin Scott Thomas), now First Desk, struggles with the consequences of an operation involving Russian intelligence.

The separate threats gradually reveal connections between professional assassins, private interests and intelligence operations that powerful people would prefer to keep hidden. Former colleagues return, old loyalties become uncertain, and the usual distinction between the failures exiled to Slough House and the professionals running MI5 becomes harder to sustain.

Adapted from Joe Country and Slough House, the sixth and seventh novels in Mick Herron's series, the six-episode season is the first to combine two books into one adaptation. It is also the first with Gaby Chiappe taking over as head writer from Will Smith.

The result is darker, more violent and closer to a conventional action thriller than its predecessors. There are some excellent reversals towards the end, and the familiar characters remain entertaining. Nevertheless, I enjoyed almost every previous season more. The series has not forgotten how to create suspense, but it increasingly seems to mistake sustained danger for sustained narrative momentum.

A Chase That Outlasts Its Mystery

The central premise of Season 6 is promising. MI5's discarded agents have become targets, and their marginal position within the Service leaves them unusually vulnerable. The Park possesses surveillance resources, armed personnel and political influence, but the slow horses cannot assume that any of those resources will be used to protect them. Their survival depends upon the same qualities that have occasionally made them useful in previous investigations: improvisation, distrust of authority and a willingness to act without permission.

By the third episode, the principal characters have been forced into a prolonged game of evasion. River and the returning Sid Baker are pursued by assassins whose professionalism makes them especially dangerous. J. K. Coe becomes involved, while other members of the team are scattered or placed under protection that may prove less reliable than it appears.

These sequences are often exciting in isolation. The problem emerges from their accumulation. For much of the middle of the season, characters move between temporary refuges, escape immediate threats and discover that their pursuers remain close behind. The danger changes location and sometimes produces serious consequences, but the underlying situation is not always transformed by what happens.

Episode 4, Lost and Found, offers an instructive contrast. River, Sid and Coe spend much of their storyline trying to escape assassins at a bowling alley. The sequence is tense, particularly because the attackers are both capable and persistent. Yet its dramatic energy comes primarily from the immediate possibility of capture or death. The broader intelligence puzzle advances less through their efforts than through events elsewhere.

Elsewhere in the same episode, Lamb meets Frank Harkness in a burger restaurant in Camden. Their confrontation is far less physically elaborate, but I found it more satisfying. Both men have information the other needs, neither is prepared to reveal his full intentions, and the apparent balance of power changes through conversation, provocation and calculated misbehaviour. Even Lamb's outrageous conduct in public serves a practical purpose. The pleasure comes from watching the two men read and manipulate each other. A seemingly careless gesture proves to have been calculated.

This was central to the appeal of Season 2's Cold War investigation. As the conspiracy developed, new information changed the meaning of earlier events. River's impulsiveness, Lamb's experience and the Service's institutional history were all part of the process through which the mystery became intelligible. The audience was learning what the confrontations meant, as well as worrying about who would survive them.

Season 6 still contains that kind of intrigue, but its distribution is uneven. The mystery frequently becomes a framework supporting the action rather than the main source of momentum. A binge-watch might make the extended pursuit feel more urgent, whereas the weekly release made its repetitions easier to notice. That explains something about my experience, but not necessarily everything about the season's structure.

Two Novels, One Overcrowded Season

The decision to combine Joe Country and Slough House complicates any judgement about whether the television series is following a weaker period in Mick Herron's novels. The adaptation does not preserve either book's structure intact, and the result cannot simply be treated as evidence of the novels' relative quality.

Director Adam Randall explained to Radio Times that Joe Country was regarded as potentially excellent material for a film, but offered comparatively little for several established television characters, particularly Lamb and Taverner. Combining it with the following novel allowed the adaptation to retain a broader ensemble.

There were also practical difficulties. Much of Joe Country takes place in a snowbound Welsh landscape, and Chiappe has discussed the problems of merging two books whose events could not simply be rearranged without consequences. The finished season draws its central pursuit from Slough House while incorporating selected material from Joe Country. Some characters and storylines have been substantially reworked or omitted.

The reasoning is understandable. Lamb and Taverner are among the television series' greatest assets, and sidelining them for much of a season would have been a substantial creative risk. The challenge is that bringing together two plots does not automatically create a richer or more coherent story.

Season 6 contains plenty of material: intersecting conspiracies, professional killers, returning characters, political manoeuvring and unresolved family relationships. Yet the need to keep so many elements in motion may explain why individual strands sometimes receive less room to develop. Instead of allowing an investigation to unfold gradually, the adaptation repeatedly moves between immediate threats and explanations delivered elsewhere.

The decision to combine the books was made before Chiappe took over, so it would be misleading to attribute this problem solely to the new head writer. Nor can we know how differently a one-book adaptation would have played. Preserving the television ensemble may nevertheless have come at some cost to the individual structures of the novels.

Adapting twice as many books has made the season busier, but not necessarily more substantial. The characters experience more danger, while the audience sometimes has less opportunity to understand the choices that brought them into it.

That also affects the series' humour. The early seasons frequently derived comedy from bureaucratic absurdity, professional vanity and the distance between MI5's official self-image and its actual behaviour. Those elements remain, particularly whenever Lamb is involved, but the political comedy has less space to establish its own rhythm. It increasingly interrupts the action rather than shaping the story around it.

Diana Taverner and the Limits of Power

Diana Taverner's promotion to First Desk may be the season's most interesting character development, although I am not entirely convinced that the writing makes the most of it.

For much of Slow Horses, Taverner was the Service's most formidable political operator. As Second Desk, she possessed the experience, institutional knowledge and ruthlessness to manipulate situations without necessarily accepting full responsibility for their consequences. She understood the informal distribution of power beneath MI5's official hierarchy and was usually more capable than the people who outranked her.

Season 4's relationship between Taverner and Claude Whelan made that distinction especially entertaining. Whelan occupied First Desk without fully understanding the institution he was supposed to control. Taverner understood it much better, but her subordinate position allowed her to influence decisions while retaining some distance from their eventual consequences. In retrospect, remaining Second Desk may have suited her particularly well.

Season 6 finally gives her the position she has been pursuing, and the promotion changes the conditions under which she operates. Taverner possesses greater formal authority, but less freedom to manoeuvre. An unofficial operation, the resulting Russian pressure and growing scrutiny of her leadership place her in situations she cannot simply redirect towards a superior. The responsibilities now belong to her.

Her television interview and the questions that follow illustrate the problem. Public authority requires her to provide explanations while the intelligence relationships behind the crisis depend upon secrecy and ambiguity. The private bargaining that might once have demonstrated her skill at manipulating others becomes considerably more dangerous when she is personally accountable for the outcome.

Taverner has not necessarily become less intelligent. She has acquired a position in which the methods that previously demonstrated her intelligence are more likely to expose her weaknesses. Second Desk rewarded her ability to manipulate responsibility; First Desk requires her to accept it.

Many capable officials are better at operating within an institution than directing it. The skills involved overlap, but they are not identical. Someone who excels at exploiting uncertainty from below may find that uncertainty much harder to tolerate when everyone expects a definitive decision from above.

The series could explore that contradiction in considerable depth. Instead, Season 6 sometimes seems unsure whether it is examining Taverner's limitations or simply making her behave less competently in order to generate another crisis. The woman who once appeared to anticipate several moves ahead now frequently reacts to problems that her earlier incarnation might have recognised sooner.

Kristin Scott Thomas remains excellent, particularly when Taverner struggles to conceal how badly events are escaping her control. But I found the character more interesting when she possessed less authority and more freedom to use it.

That is also a recurring argument of Slow Horses itself. Institutional rank is an unreliable measure of competence, and promotion does not necessarily place someone where their abilities are most useful. Taverner's success has exposed a different kind of professional limitation from the failures that originally consigned Lamb's agents to Slough House.

When Violence Replaces Intrigue

The increasing darkness of Season 6 is not entirely new. Slow Horses has contained brutal violence since its beginning, and the cumulative losses suffered by the characters make it reasonable that the series should become more sombre as it develops. These people have experienced betrayal, injury and death often enough that returning indefinitely to the lighter tone of the opening seasons would begin to feel artificial. What has changed is the balance between violence and the rest of the drama.

In my review of Season 3, I criticised its prolonged action climax for allowing an extended firefight to displace the more interesting institutional conflict. That season had exposed how MI5's leadership could use secrecy and violence to contain the consequences of its own mistakes. The finale demonstrated the danger physically, but the action eventually occupied more space than the institutional argument seemed to require.

Season 4 recovered much of the balance through River's investigation into his family history. Its violence emerged from an inquiry into old intelligence operations and the people whose lives had been shaped by them. Season 5 again offered an elaborate conspiracy, this time involving adversaries who understood how to manipulate the predictable reactions of British institutions. I found its execution less satisfying than its central idea, but the idea itself was strong.

Season 6 is less distinctive because its dominant dramatic mechanism is simpler. The slow horses are being hunted, and their immediate problem is survival. The political intrigue explains why that situation exists, but the characters spend comparatively little time investigating it before being forced into another confrontation.

There is nothing inherently inferior about a well-made action thriller. The assassins are convincingly dangerous, several pursuits are effective, and the threats are given greater emotional force by our familiarity with the characters. Viewers who particularly enjoy the series' action may reasonably find this one of its strongest seasons.

My reservation concerns what becomes less prominent when that action takes over. Slow Horses originally drew much of its humour and intelligence from the interaction between institutional dysfunction and personal failure. Lamb's team was not secretly Britain's most capable collection of agents. Its members possessed narrow skills, serious weaknesses and a remarkable ability to stumble into situations where those skills unexpectedly mattered. Meanwhile, the supposedly competent officers at the Park were often engaged in protecting their careers rather than protecting the country.

Their parallel failures gave the series its satirical force. It could be amusing and disturbing at the same time because the distance between success and failure inside MI5 was frequently determined by status, political connections and control of the official account.

Season 6 retains those ideas, but they are less central to the viewing experience. The series increasingly resembles a conventional thriller populated by unusual characters, rather than an institutional satire whose conflicts occasionally become violent.

The distinction does not require the series to return to a less dangerous world. Its characters can grow older, acquire scars and confront more capable enemies. But if those developments leave too little room for the intelligence work and bureaucratic manoeuvring that gave the earlier seasons their identity, the series risks becoming more interchangeable with other thrillers even as its production becomes more ambitious.

An Ending That Recovers the Old Slow Horses

Despite my reservations, the season improves as its various storylines converge. The closing episodes restore more of the concealed agendas, shifting loyalties and calculated reversals that I found so satisfying in earlier seasons. Information becomes a source of power again, rather than merely an explanation for why the characters are in danger.

Lamb is particularly effective when the story gives him opportunities to negotiate, deceive and exploit other people's assumptions. Gary Oldman's performance continues to make the character entertaining, but his most interesting quality is not his willingness to insult everyone around him. It is his ability to understand what other people want and how far they are prepared to go to obtain it.

River also benefits from the more personal dimensions of the concluding episodes. His recklessness has always been tied to a desire to prove himself, but the family history developed in previous seasons gives his choices greater emotional weight. Jack Lowden continues to make him sympathetic without disguising how frequently he misjudges people and situations.

The ending contains several effective twists, and I would not want to diminish their impact by describing them here. They demonstrate that the series can still surprise through shifting relationships and discoveries about characters we thought we understood. Some of the best moments rely less on physical confrontation than on a sudden change in what one person knows about another.

That recovery also makes the preceding episodes more frustrating. The ingredients for a stronger season were present throughout. I would have preferred the political and personal intrigue to develop more consistently alongside the danger, rather than having so much of the middle dominated by pursuit.

I still enjoyed Season 6. The performances remain strong, the established characters have enough history to sustain genuine emotional stakes, and the final episodes contain much of what originally drew me to the series. But I would place it below almost all its predecessors, particularly Season 2 and Season 4, whose investigative structures gave their violence a more satisfying context.

Taverner's promotion offers an unintended summary of the season. She has gained the authority she spent years pursuing, but with less freedom to use it. Slow Horses has undergone something similar. Its action has become bigger and more relentless, while the space for the intrigue that once gave that action its meaning has narrowed.