Slow Horses centers on Slough House, the dumping ground for MI5’s rejects. These are the agents who’ve botched assignments, embarrassed their superiors, or otherwise made themselves unwelcome in the sleek, high-stakes world of London espionage. Instead of saving the world, they’re saddled with paperwork, coffee runs, and a boss who treats them with utter disdain.
That boss? Jackson Lamb, a washed-up but brilliant spymaster with a penchant for sarcasm, questionable hygiene, and the uncanny ability to spot threats the rest of MI5 overlooks. Slow Horses takes this band of misfits and throws them into the fire of espionage, proving that even “losers” have their day.
Humor, Humanity, and Tension
At its core, Slow Horses is about redemption—or the lack thereof. The show doesn’t shy away from its characters’ flaws, nor does it try to glamorize their world. Instead, it leans into the absurdity of their situations, blending dark humor with moments of genuine vulnerability.
The writing is whip-smart, capturing the essence of Herron’s novels while adapting them for a visual medium. The tension is palpable, and the stakes feel real—even when the Slough House crew seems hilariously out of their depth. This balance between comedy and suspense is a rare find, and it’s a huge reason why the series resonates.
Meet the Misfits: Characters Who Steal the Show
Jackson Lamb (Gary Oldman)
Let’s start with the obvious: Gary Oldman as Jackson Lamb is pure casting genius. Lamb is equal parts despicable and magnetic, a gruff mentor who insults his team with abandon but ultimately protects them with ferocity. Oldman brings depth and complexity to the role, making Lamb a character you love to hate—and maybe even respect. Quite frankly, the relish with which he tackles this role only amplifies the viewing pleasure for us.
River Cartwright (Jack Lowden)
The golden boy who fell from grace, River is the audience’s entry point into Slough House. Jack Lowden perfectly captures River’s frustration and determination, portraying a man who’s desperate to prove he’s more than his failures. His clashes with Lamb are a highlight, full of biting humor and simmering tension.
Diana Taverner (Kristin Scott Thomas)
Scott Thomas brings her signature poise and sharp wit to Dianna Taverner, the steely and calculating second-in-command at MI5. Known as “Lady Di,” Taverner operates with a mix of ruthless efficiency and political savvy, always ready to outmaneuver allies and adversaries alike. Scott Thomas imbues Taverner with an air of authority and underlying menace, making her a commanding presence in every scene, especially those with Jackson Lamb.
David Cartwright (Jonathan Pryce)
Jonathan Pryce shines as David Cartwright, the wily and insightful grandfather of River Cartwright. A retired intelligence officer with a vast well of experience and secrets, Cartwright senior serves as both mentor and occasional antagonist to his grandson. Pryce plays the role with understated charm, balancing warmth with an edge of mystery, reminding viewers that even in retirement, spies never truly hang up their tradecraft.
The Rest of the “Horses”
From the hilariously sleazy Roddy Ho (Christopher Chung) to the perpetually nervous Louisa Guy (Rosalind Eleazar) and the perfect foil to Lamb, Catherine Standish (Saskia Reeves), each member of Slough House adds their own flavor to the mix. The ensemble cast is a masterclass in chemistry, bringing Herron’s characters to life with wit and depth.