Slow Horses Season 4: The Gary Oldman Show

There is a specific kind of prestige drama that Apple TV+ has become unusually good at greenlighting and unusually good at protecting from the streaming-economy pressure to be louder, larger, or more algorithm-friendly. Slow Horses, Will Smith’s adaptation of Mick Herron’s novels about a team of disgraced MI5 agents relegated to a dead-end unit called Slough House, is the clearest example of this pattern. Season 4, which aired in September and October 2024, was the show’s strongest to date.

A year on, I want to argue for why this show, which has gathered little cultural conversation for a show of its quality, is the most consistently-executed piece of ongoing television drama currently running.

What the show does right

Slow Horses is, structurally, the opposite of most streaming-era prestige drama. Seasons are six episodes. Plots resolve inside each season. Characters grow gradually across seasons without requiring the viewer to have memorised the prior-season cliffhangers to follow the current material. The show’s run times are tight (forty-five to fifty minutes per episode, in a format that increasingly runs toward seventy). The pacing assumes a viewer who wants to be respected.

Season 4 brings the show into its fully mature register. The season’s central plot, a bombing in a London shopping centre that ties to the estranged father of Jack Lowden’s River Cartwright, delivers genuine emotional weight without losing the show’s specific comic-thriller tone. The writing, by showrunner Will Smith (the screenwriter, not the actor), is the tightest it has been.

Gary Oldman, sustaining

Gary Oldman’s Jackson Lamb, the flatulent, alcoholic, brilliant head of Slough House, has become one of the defining television roles of the 2020s. Oldman has now played Lamb across four seasons and is, remarkably, getting better at it. Season 4’s Lamb is quieter than the earlier versions. The specific physical tics, the flask, the raincoat, the stained jumper, the cigarette, are all still present, but the performance underneath has developed a specific texture of grief and exhaustion that was not as visible in earlier seasons.

Lamb, in Season 4, has begun to slow down. The reasons, which the show handles with a specific respect for the viewer’s intelligence, have to do with his declining health and his specific professional relationships with his old MI5 generation. Oldman plays this decline without showy markers. The scene in which Lamb, alone in his office, reviews a photograph of his old team, is the specific moment the season’s emotional arc turns, and Oldman plays it in almost complete silence.

Jack Lowden, carrying the other half

Jack Lowden’s River Cartwright, the show’s closest thing to a protagonist, has a specific family-history subplot in Season 4 that the earlier seasons had gestured at but not fully activated. River’s father, previously believed dead, is revealed to still be alive and to be, complicatedly, the antagonist the season’s plot turns on. Lowden plays River’s processing of this revelation across the season’s six episodes as a specific cumulative trauma.

The scene between River and his grandfather David Cartwright (Jonathan Pryce, who has been the show’s moral anchor across seasons) in the season finale is the emotional resolution the show has been patiently earning for three seasons, and it lands. Pryce, in what is almost certainly his last extended screen work (he is in his late seventies and has indicated semi-retirement), gives a performance that should have been the year’s supporting-actor conversation.

The ensemble around them

Slow Horses has, across four seasons, built one of the strongest regular ensembles on television. Kristin Scott Thomas as Diana Taverner, the MI5 deputy director whose relationship with Lamb is the show’s most delicate ongoing dynamic, gets expanded material in Season 4 that she handles with her usual precision. Saskia Reeves as Catherine Standish, Lamb’s long-suffering secretary whose specific loyalty to him is the show’s quietest emotional through-line, delivers a series-best performance in the season’s second half.

Newer cast members, including Ruth Bradley as Emma Flyte, a rival operative introduced this season, continue the show’s pattern of bringing in strong supporting performers who can hold their own against the established cast. The ensemble is working at a level that very few ongoing dramas can sustain four seasons in.

What the show refuses to do

A specific thing worth noting: Slow Horses has not, across four seasons, been tempted into any of the structural moves that are currently breaking other long-running prestige dramas. It has not expanded its universe into spinoffs. It has not introduced “world-building” that the viewer is expected to keep track of. It has not added cameo characters from the MI5 hierarchy with the promise of further development.

It has stayed, episode after episode, with the same dozen or so core characters, in the same set of London locations, telling tight six-episode stories that resolve. This is a formal discipline that Apple TV+ has allowed the show to maintain, and that the show has used well.

Season 5

Season 5, as of this writing, has completed filming and is scheduled for late 2025 release. The source novel is London Rules, which Mick Herron’s readers will know is one of the series’ strongest entries. The adaptation should be straightforward. I will be in my armchair on the premiere night.

Apple has, at this point, committed to the show through at least Season 7, which means we are guaranteed further adaptations of Herron’s books for at least another three years. This is, for any prestige-drama fan, genuinely good news.

Watch Season 4 across a weekend. It is one of the best six-episode blocks of television of the decade, and the show keeps quietly getting better.