Slow Horses Season 6 Review: MI5's Messiest Spies Return

This sixth outing throws the dysfunctional MI5 rejects of Slough House back into the espionage world's smoke and mirrors, with Gary Oldman's gloriously repulsive Jackson Lamb still presiding over his kingdom of misfits like a flatulent emperor. River Cartwright (Jack Lowden) is once again caught between doing the right thing and surviving the fallout, while Kristin Scott Thomas's Diana Taverner schemes from the upper floors with her usual icy efficiency. The season leans hard into the show's signature blend of bureaucratic absurdity and genuine mortal danger, with sinister forces lurking behind every corner and Hugo Weaving's Frank Harkness looming as a threat that refuses to stay buried. The supporting players - Saskia Reeves's Catherine Standish, Christopher Chung's insufferable Roddy Ho, Rosalind Eleazar's Louisa Guy, and Aimee-Ffion Edwards's Shirley Dander - all get their moments to shine in a season that knows exactly what its audience came for.

Here's the thing about Slow Horses: it has no business being this consistent. Six seasons in, most shows are either recycling old tricks or blowing up the formula for shock value. This one just quietly keeps doing what it does best - mixing le Carré-grade paranoia with workplace comedy that would make The Office blush. The result is a season that feels like slipping into a worn leather jacket: familiar, comfortable, and somehow still capable of catching a knife to the ribs when you least expect it.

Oldman continues to be the show's secret weapon and its beating, belching heart. Jackson Lamb is a character who should be unbearable - and he is, deliberately - but Oldman finds the weary humanity underneath the crust. Every eye roll, every barbed insult, every scene where he's clearly three steps ahead of everyone in the room is a masterclass in doing the most by appearing to do the least. Watching him verbally dismantle a superior officer is worth the subscription alone.

Lowden's River remains the perfect foil, all earnest ambition and terrible decisions, and the show wisely keeps him front and center. The push-pull between his need to prove himself and Lamb's total refusal to let him is the engine that keeps this thing humming. Meanwhile, Scott Thomas glides through every scene like a shark in a power suit - Taverner is still the most quietly terrifying person on television, and we mean that as the highest compliment.

What's impressive about Season 6 is how it manages to feel both episodic and cumulative. The mysteries of the week matter, but the wounds from previous seasons haven't healed. Characters carry their scars - sometimes literally - and the show respects its own history without drowning in it. The pacing is tight, the dialogue crackles, and the twists land because they're earned rather than shock for shock's sake.

If there's a criticism, it's that the show occasionally gets too comfortable with its own rhythms. Certain beats feel familiar, and you can sometimes predict who's going to get double-crossed before it happens. But when the execution is this good, familiarity breeds contentment rather than contempt. This is comfort food for people who like their comfort food served with a side of betrayal and existential dread.

Pros:

• Gary Oldman delivering another career-high turn as the unforgettable Jackson Lamb
• A cast that fires on all cylinders, from Lowden's anxious River to Chung's hilariously insufferable Roddy
• Sharp, quotable dialogue that balances black comedy with genuine tension
• A season that honors the show's history without getting bogged down in it

Cons:

• Some plot beats feel a touch too familiar for longtime viewers
• Certain twists telegraph themselves before the reveal
• You'll inevitably want to binge it all in one sitting, which is bad news for your sleep schedule

Slow Horses Season 6 is proof that a show can stay great by simply refusing to coast. It's gritty, hilarious, and sneakily emotional, with a cast that makes every scene feel lived-in and a lead performance that remains one of the best things on any screen anywhere. Is it the best season yet? Hard to say - the bar was already absurdly high. But it's absolutely worth your time, and if you're not already watching, you now have six seasons of catching up to do. Consider that a gift, not a chore. Stream it now on Apple TV+.