Slow Horses' 13 Slough House Agents Explained

Given the various characters' reasons for being at Slough House and the stakes often involved in their missions, this situation has dire implications for public safety.

Slough House is overseen by the grizzled, flatulent, and surprisingly effective Jackson Lamb (Gary Oldman) – a former field agent who, despite appearances, remains an extremely capable operator. Rounding out his team are a range of misfits whose transgressions range from accidental idiocy to antisocial personality.

While Slough House is deliberately situated away from MI5's main base of operations at The Park, the team is still part of the service and has been involved in many high-profile operations. As such, understanding its membership is crucial to unpacking the show's wider story ahead of Slow Horses season 6.

Jackson Lamb

Played by: Gary Oldman

The slovenly, rude, and brilliant leader of the Slough House crew, Jackson Lamb is a complicated and contradictory character. Having requested the post after an operation to murder the former First Desk, Charles Partner, following the latter's defection to the Soviet Union, Lamb spends his time drinking, smoking, eating Chinese takeaway, and abusing any of his colleagues that he comes into contact with.

However, for all his many, many faults, Lamb retains a keen eye for detail and an almost unparalleled ability to play the strange games involved in spycraft. Throughout Slow Horses, Lamb is almost always several steps ahead of his colleagues and has proven capable of manipulating people and events to suit his agenda.

Despite his declared nihilism, his mask occasionally slips to reveal genuine affection for his underlings – especially Standish, whose brief departure from Slough House clearly weighed on him.

River Cartwright

Played by: Jack Lowden

An earnest, dutiful spy, River Cartwright remains desperate to prove himself after being set up for failure in the training exercise that earned him his place in Slough House. It was actually his impressive ability to tail Diana Taverner undetected that warranted his exile from The Park. Nonetheless, Slow Horses' River has some critical flaws that have led to some of the show's biggest blunders.

River mixes determination and occasional flashes of brilliance with an inability to navigate the Machiavellian world of MI5. The often-promising agent has also proven to be impulsive, relentless, and somewhat uncontrollable, frequently going rogue and pushing missions past the point of reasonable feasibility.

Slow Horses season 4 further fueled River's complicated personal relationship with MI5 with the reveal of his father, Frank Harkness. Harkness, a former CIA operative and frighteningly ruthless mercenary, has historically worked with MI5 despite his unethical methods. Frank is set to return in Slow Horses season 6, promising further exploration of River's loaded family dynamic.

Catherine Standish

Played by: Saskia Reeves

Behind Lamb himself, Standish regularly proves herself to be one of Slough House's most capable operators. Ostensibly working as the building's office administrator, she is also very capable in the field, variously interrogating suspects, expertly negotiating terrifying hostage situations, and tracking down terrorists throughout Slow Horses seasons 1 to 3.

However, like everyone at Slough House, Standish is also flawed. A recovering alcoholic, she retains an almost fanatical loyalty to her ex-employer, Charles Partner. This leads her into direct conflict with Lamb, who is frustrated by her inability to see the truth about her old boss. When he finally told her the blunt truth about Partner, Standish quit her job at the end of season 3.

Yet she continued to be pulled into the Slough House action as season 4 saw River deposit his declining grandfather with Standish for his safety. After being a begrudging participant for most of the season, Standish finally returned to Slough House, much to the satisfaction of Lamb, who never completed her exit paperwork to begin with.

Louisa Guy

Played by: Rosalind Eleazar

Sent to Slough House after a tailing operation ended in disaster, Louisa Guy is one of the most traumatized members of the team. Initially frosty towards her colleagues, she started a relationship with Min Harper that ended in heartbreak when Min was murdered in Slow Horses season 2. Despite the hardship she's faced, Louisa is easily one of Slough House's most capable agents.

Her competence led to her forming a firm, though sometimes awkward, friendship with River, with the pair proving a formidable partnership in the field. Nonetheless, season 5 opened with Louisa departing on a six-month mental health leave that she privately told River she intended to be permanent. She was then absent from Slow Horses season 5 through to the end.

Thankfully, Rosalind Eleazar is set to reprise her role as Louisa in Slow Horses season 6, which will hopefully see the character return to Slough House in full capacity.

Roddy Ho

Played by: Christopher Chung

A talented but endlessly obnoxious computer expert, Roddy Ho is a source of huge frustration for his Slough House colleagues. Oozing superiority, Roddy can't help but rub people up the wrong way. In fact, while he is highly technically capable, his personality is his main obstacle in progressing further within MI5. The only reason he remains a Slow Horse is the rest of the agency's refusal to work with him.

However, for all his faults, Roddy has still shown himself to be occasionally courageous, playing a key role in the field in both seasons 2 and 3. Season 5, then, revealed the insecurity and loneliness behind his bravado when Roddy believed he had a girlfriend who proved to have pursued him only to breach the data protections of MI5.

The rest of Slough House recognizes his poorly disguised fragility. Despite finding him insufferable and knowing the true reason he has been relegated to Slough House, no one has told him, instead allowing him to believe that he is just "too good" for MI5, a lie that has stoked his ego even further.

Shirley Dander

Played by: Aimee-Ffion Edwards

An agent who struggles with both anger management and addiction, Dander encapsulates the dysfunction on display at Slough House. Although she has proven to be more capable than many of the team, fighting Andre Chernitsky in season 2 and taking on an entire team of mercenaries in season 3, Dander is also her own worst enemy, even getting fired by Lamb for being found at a crime scene with narcotics.

As of the season 3 finale, she had formed a tentative partnership with Marcus Longridge, with the pair helping to moderate each other's worst tendencies. However, Marcus was killed in the season 4 finale, putting Shirley in her darkest place yet ahead of season 5. Though she was the first to notice the danger Roddy was in, she was initially dismissed as being paranoid after Marcus' death.

While she certainly has her share of vulnerabilities, Shirley proved to be an asset to the team throughout Slow Horses season 5.

J.K. Coe

Played by: Tom Brooke

Coe is eccentric, even for the Slough House crowd. Having formerly worked in the Psychological Evaluations department at the Park, Coe was reassigned to Slough House due to the severe PTSD that inhibited him from doing his job. At Slough House, Coe is characterized as being a man of few words and unpredictable behavior.

Nonetheless, his perceptive and analytical thinking has already proven to be a major asset to the team since his arrival in Slow Horses season 4. Most recently, Coe's deep knowledge of national destabilization strategies helped the Slough House team pursue the looming threat in the chaotic season 5.

Marcus Longridge

Played by: Kadiff Kirwan

Despite being offered the opportunity to join Duffy's unit of "Dogs", Marcus Longridge found himself at Slough House after struggling with a gambling addiction. Although he, like Dander, is capable in the field, his gambling proved to be a major obstacle, with his attempts to hide it from his wife a source of major tension.

He played a key role in multiple Slough House operations, liaising with Louisa Guy in season 2 and Dander in the explosive season 3 finale. He also kills Nick Duffy in a dramatic season 3 showdown, proving that he was one of the most dangerous members of Slough House the show had seen.

Even so, Slow Horses season 4 ended with Marcus being killed by Patrice, one of Frank Harkness' mercenaries and a half-brother of River's. Marcus' death was the latest evidence that no Slow Horses character is safe, as the show has not been hesitant with unexpected character departures throughout its run.

Moira Tregorian

Played by: Joanna Scanlan

Moira Tregorian was introduced as Catherine Standish's temporary replacement in Slow Horses season 4. An MI5 record keeper exiled to Slough House by then-Director General of MI5, Claude Whelan, Moira was desperate to find her way back to the Park. Lamb, equally uninterested in her presence at Slough House, offered to aid in her return in exchange for her help with River's season 4 trip to France.

She left Slough House after successfully blackmailing Claude for her job back, but the character is set to return in Slow Horses season 6, where the trailer has revealed that she will be on the "kill list" targeting all past and present employees of Slough House.

Min Harper

Played by: Dustin Demri-Burns

A bumbling and fundamentally gentle member of the team, Min Harper was relegated to Slough House after accidentally leaving a dossier of top-secret documents on a train – a mistake that reveals much about his personality. Although he struggled to get over the blunder (which ultimately led to a divorce from his wife), he found solace in a new relationship with fellow Slow Horse Louisa Guy.

Tragically, their time together was cut short when Min Harper is dramatically murdered midway through season 2, an event that kick-started Louisa's own loss-fueled storyline.