Slow Horses Characters Ranked as Season 6 Hype Builds

Slow Horses Just Scored 9 Emmy Nods, and Season 6 Is Right Around the Corner

My Tier List Overview

Here's the full breakdown before I get into the reasoning:

• S Tier: Jackson Lamb, River Cartwright, Catherine Standish
• A Tier: Diana Taverner, Roddy Ho, Shirley Dander
• B Tier: Louisa Guy, Marcus Longridge, Sid Baker
• C Tier: J.K. Coe, David Cartwright, Peter Judd
• D Tier: Jed Moody, Spider Webb

S Tier: The Characters I'd Watch a Spin-Off About

Jackson Lamb. Gary Oldman just built one of the most quietly disgusting-looking characters on TV right now — the same stained mac, the same unwashed hair, the same office that smells bad through the screen — and somehow that's exactly what makes him magnetic. The costume and grooming choices are doing so much work here: he looks like he's actively rotting at his desk, and then he opens his mouth and delivers the sharpest, cruelest, funniest read in the room. What gets me every single time is the whiplash — one scene he's humiliating Ho over something petty, the next he's quietly, almost invisibly protecting one of his agents from MI5 higher-ups, and he'll never admit that's what he's doing. The Charles Partner backstory is the one that really got me; you realize this man has been carrying real grief under all that contempt for years, and he'd rather die than say it out loud.

River Cartwright. River works for me because he's constantly caught between two versions of himself — the golden-boy legacy agent he was raised to become, and the guy who keeps failing spectacularly in front of people who already doubt him. Jack Lowden plays that tension so well that even his posture changes depending on who's in the room with him. His scenes with his grandfather David hit differently once you know how much River idolizes him, and once that relationship gets complicated (no spoilers, but it does), it's some of the best acting in the whole show. He's also just fun to root for — reckless, a little arrogant, but never in a way that makes you stop wanting him to win.

Catherine Standish. Catherine is the character I underestimated the most on my first watch and now can't stop thinking about. She dresses like the most buttoned-up person in the building — muted colors, nothing flashy, always composed — and that restraint is basically a costume choice that tells you everything about how hard she's worked to hold herself together. Her sobriety storyline never gets played for cheap drama; it's treated with real weight, and it makes her one of the few characters whose calm actually feels earned rather than written in. The scenes where she quietly outmaneuvers someone twice her rank without raising her voice are some of my favorite moments in the entire series — she wins by being underestimated, every time.

A Tier: Brilliant, Just a Notch Below

Diana Taverner. Kristin Scott Thomas plays Lady Di as someone who's always three moves ahead, and the show is smart enough to never fully let you trust her — or fully let you hate her either. Her power suits and clipped delivery are doing as much storytelling as her dialogue.

Roddy Ho. Ho is polarizing, and that's exactly why he works. The self-mythologizing, the oversized confidence, the genuinely useful hacking skills buried under all the delusion — he's a character built to be laughed at and rooted for in the same scene, and his storyline with Tara actually gave him some real vulnerability for once.

Shirley Dander. Shirley's volatility could easily have made her a one-note character, but she's got real depth under the aggression, especially in how the show handles her grief over Min. Her chemistry with Marcus is one of the more low-key satisfying partnerships in the cast.

B Tier: Reliable, Not Quite Standout

Louisa Guy. Louisa's arc has been quietly one of the better ones — she's competent, sharp, and has believable relationships, but she rarely gets the standout episode the way Lamb or River do.

Marcus Longridge. Steady, capable, and a good scene partner for Shirley, but Marcus is more of a solid supporting piece than someone I'm actively excited to see on screen.

Sid Baker. Her return, with Olivia Cooke confirmed back for Season 6, is genuinely one of the more interesting twists in the show's recent history, and it bumps her up from where she'd otherwise sit — a character who was compelling in Season 1 and is now getting a real second chapter.

C Tier: Solid Supporting Cast

J.K. Coe. The near-silent, traumatized ex-psychologist is an interesting swing, but he works better as a plot device than as someone I'm emotionally invested in.

David Cartwright. River's grandfather carries a lot of weight as the old-guard MI5 legend River is desperate to live up to, and the reveals about his real legacy add some good complexity — he's just not someone I look forward to a scene with the way I do River himself.

Peter Judd. He's a fun, sleazy jab at a certain type of populist politician, and it's an entertaining performance, but he mostly exists to be insufferable rather than someone with much depth underneath.

D Tier: The Ones Who Didn't Make It Far

Jed Moody. His early exit was genuinely one of the show's better shock moments, but he wasn't around long enough to become more than "the guy who died."

Spider Webb. Great as a punchable rival — smug, ambitious, always looking for a shortcut — but he's more of a functional obstacle for River than a character I care about beyond that.

What Season 6 Could Change

The timing on this list feels right, because Season 6 is already reshuffling how I feel about a few of these placements. Sid Baker's return after being presumed dead since Season 1 is a huge deal for longtime fans, and the trailer's final shot of her back facing River suggests her storyline is about to get a lot bigger. On top of that, Diana Taverner is pulling the whole team into a retaliation-and-revenge plot that puts them on the run, and Hugo Weaving is back as River's father, Frank Harkness — which means River's arc might be about to get even heavier. I'll probably revisit this ranking once the season wraps.

How I Made This Into an Actual Chart

Once I had my rankings sorted out in my head, I made it into an actual tier list image using a free tool I stumbled on called TierMakerPro — no sign-up, just open their Slow Horses tier list template, drag each character into a row, and export it as a PNG when you're done. It already had most of the character portraits loaded in, and you can swap in your own images too if you want a custom cast photo. Took me less than ten minutes to make the version I posted on my socials — you can grab the same TierMakerPro template and build your own in about the same time.

So, Where Do You Put Lamb?

That's my read on the Slough House roster going into Season 6. How would you sort your own Slow Horses characters ranked list — and is there anyone here you'd move up or down a tier? Drop your rankings in the comments, I'd genuinely love to see how differently people sort this cast.

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FAQ

How many main characters does Slow Horses have? The core Slough House ensemble has grown to around a dozen recurring agents and handlers across six seasons, alongside a rotating cast of MI5 characters like Diana Taverner and various "First Desk" officials.

Who's the better lead, Jackson Lamb or River Cartwright? They serve different roles — Lamb is the show's cynical moral compass and comic engine, while River is its emotional throughline. Most fans (myself included) rank Lamb slightly higher just because Gary Oldman's performance carries so much of the show's tone.

Is Sid Baker really back in Season 6? Yes — Apple TV confirmed Olivia Cooke is returning as Sid Baker for Season 6, despite her character being shot and presumed dead back in Season 1.

Is TierMakerPro free to use for a tier list like this? Yes, it's free with no account required — you open a template, drag the characters into tiers, rename or recolor the rows if you want, and export the finished image as a PNG.

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