Slow Horses Season 4 Review: Gary Oldman’s Spy Drama Remains Must-Watch TV

Four seasons in, Slow Horses has quietly become the best spy show on television. Adapting Mick Herron’s Slough House novels, the series continues to follow the misfit MI5 agents banished to a bureaucratic dead end under the supervision of Jackson Lamb, the most disgusting and brilliant spymaster in fiction. Gary Oldman remains absolutely phenomenal in the role, and Season 4, based on Herron’s “Spook Street,” delivers the show’s most emotionally resonant chapter yet.

How We Reviewed: We grounded this review in noting how character development serves or undercuts theme and viewing all available episodes before publishing. Ratings reflect full-season viewing, critical analysis, and production quality assessment. Our recommendations are editorially independent and not influenced by advertising.

The Bombing

Season 4 opens with a shopping center bombing that immediately raises the stakes beyond anything the Slow Horses have previously faced. The investigation pulls River Cartwright (Jack Lowden) deeper into his family history when his grandfather, former MI5 legend David Cartwright (Jonathan Pryce), becomes connected to the case through circumstances that suggest either conspiracy or cognitive decline. The collision of personal loyalty and professional duty gives the season a poignancy that earlier entries, for all their excellence, did not quite achieve.

Jack Lowden delivers his strongest performance as River, a young agent whose competence has never been in doubt but whose emotional maturity is tested when the people he loves most are threatened. His scenes with Jonathan Pryce are the season’s emotional centerpiece — a grandson watching his hero deteriorate while suspecting that the deterioration may be hiding something more deliberate.

Lamb at His Best

Gary Oldman’s Jackson Lamb remains one of the great television characters. Flatulent, slovenly, casually cruel to his subordinates, and possessed of an intelligence that his appearance is designed to conceal, Lamb is a creation that should not work on paper. Oldman makes him magnetic. Season 4 gives Lamb slightly more vulnerability than previous seasons, hinting at the cost of decades in the intelligence world without ever softening him into sentimentality.

The ensemble continues to deepen. Saskia Reeves’s Catherine Standish gets material that explores her recovery and resilience. Rosalind Eleazar’s Louisa Guy takes on more responsibility. Christopher Chung’s Roddy Ho remains hilariously oblivious. Each season adds layers to characters who could easily remain stock types, and Season 4 continues that pattern with skill.

The Antagonist

Hugo Weaving joins the cast as a figure from the intelligence world’s past whose connection to the bombing unfolds across the season. Weaving brings an icy authority to the role, and his scenes with Oldman crackle with the energy of two veteran actors relishing their material. The show’s antagonists have always been its weakest element compared to its heroes, but Season 4 provides a villain with genuine menace and motivation.

Craft and Pacing

At six episodes per season, Slow Horses maintains the tight pacing that distinguishes it from bloated streaming dramas. Every scene matters. Every conversation advances character or plot or both. The show never wastes a moment, and the brisk runtime means there is no filler — just propulsive, intelligent storytelling that respects the audience’s time.

The London locations are used beautifully, and the show’s unglamorous depiction of intelligence work — the bureaucracy, the interoffice politics, the sheer tedium punctuated by moments of lethal danger — feels more authentic than any Bond film. Slough House itself, with its peeling wallpaper and malfunctioning heating, is a character in its own right.

Verdict

Slow Horses Season 4 is another triumph. The show’s consistency is remarkable — four seasons without a significant dip in quality. Gary Oldman is operating at the highest level, the ensemble is excellent, and the adaptation of Herron’s novels continues to be one of television’s most reliable pleasures. If you are not watching Slow Horses, you are missing one of the best shows currently airing.

Rating: 9/10

For more espionage television, check out our guide to the Best Spy Thriller Shows Streaming and our Apple TV Plus Best Shows Guide.