Six seasons in, and the worst critical score this Apple TV spy series has ever posted is 95%. That’s the floor. For most long-running dramas, that number would be the ceiling, hit once in a peak year and never touched again.
Espionage shows have a long history of burning bright and then flaming out after two or three strong runs. There are only so many ways to keep a spy story surprising once the audience knows the rhythms. This one found a workaround.
The show is Slow Horses, adapted from Mick Herron’s Slough House novels, and it takes the glossy super-spy image and drops it down a flight of stairs. No immaculate agents saving the world in tailored suits.
Instead you get a cluster of disgraced MI5 operatives shoved into the agency’s bureaucratic dumping ground, stuck marinating in their own career-ending mistakes under the watchful and permanently annoyed eye of Jackson Lamb, played by Gary Oldman.
The scores, season by season
Since its 2022 debut, critics and audiences have landed in roughly the same place on this one, which almost never happens. The first season opened at 95% from critics and 88% from audiences.
Then came the part where shows usually stumble. Season 2 posted a perfect 100% from critics and 90% from audiences, proving the premise had enough underneath it to carry a second story.
The third season slipped a hair to 98% from critics, with 89% from audiences. Season 4 climbed right back to 100%, again with an 89% audience score, and its Rotten Tomatoes consensus went out of its way to note the series showed “no signs of fatigue.”
Season 5 is the one that split people. It still landed at 96% from critics, though the audience score dipped to 82%, the lowest the show has recorded. In most TV neighborhoods, that’s a victory lap.
Season 6 currently sits at a perfect 100% from critics, with the audience number still TBA. Three seasons at 100% so far. The overall series Tomatometer stands at 98%.
Season 6 has a date
Apple TV renewed the show for a sixth season back in October 2024, just days after the fourth season’s finale aired. Nobody was shocked. The series has been one of the streamer’s steadier prestige plays.
Season 6 premieres September 16, 2026, and the early reviews have been excellent, which is how that perfect score got there in the first place.
Why the floor never dropped
From the opening episodes, the show understood that its people matter as much as its plotting. The MI5 rejects work precisely because they’re the opposite of the polished operatives the genre usually hands you.
Everyone at Slough House contributes something, but pretending Oldman isn’t stealing the thing outright would be dishonest. Lamb reads at first like a foul-mouthed, miserable manager with zero interest in his staff. Under the insults and the genuinely repulsive habits sits an exceptionally sharp spy who knows exactly how to move through a dangerous world.
The tonal footwork helps too. One minute it’s funny, the next it’s tense, and the switch never feels forced. And rather than photocopy whatever worked last time, each season hands the Slough House crew a fresh crisis to survive. It doesn’t get boring.
The adaptation itself deserves credit. Herron’s books are the kind you don’t put down, and the show keeps that while adding personality that a lazier version would have flattened. The source novels won the CWA Gold Dagger Award, and the series treats them like they earned it.
Slough House is where British intelligence sends the people it would rather forget. Six seasons later, it’s the address that hasn’t dipped below 95%.
