Slow Horses season 5 concludes with dramatic events that reshape MI5 and Slough House. Although this season followed a smaller, more contained storyline, the finale delivered major revelations. River Cartwright achieves a measure of redemption after earlier blunders, Jackson Lamb once again shows his hidden brilliance, and MI5 undergoes a significant leadership shift. These developments create a foundation for major changes in season 6.
Diana Taverner Rises As Whelan Falls While Libyan Plotters Reveal Their Motives
Claude Whelan’s time as First Desk reaches an end after a season marked by distraction and poor decision-making. The terrorists do not even recognize him as the true authority and instead ask for Diana Taverner. Lamb later uses a recording to pressure Whelan into resigning in order to protect Slough House. Diana then ascends to First Desk, a position she has pursued since season 1. Her experience makes her highly capable, yet her leadership will introduce new political tensions.
Kristin Scott Thomas as Diana Taverner and Gary Oldman as Jackson Lamb (Slow Horses/Apple TV)The attackers who terrorize London are eventually revealed as Libyans who once participated in peaceful protests before radicalizing. Their anger stems from the United Kingdom’s withdrawal from Libya, a decision influenced by Whelan’s recommendations. Their goal is to punish him publicly for the consequences of that policy. Their actions cause many casualties, including unintended victims, but Lamb’s team ultimately prevents the assassination of Mayor Jaffrey and protects Whelan from being killed.
Jackson Lamb’s Painful Past, River’s Stalled Future And Slough House’s Uncertain Survival Emerge
One of the most emotional moments in the finale occurs when viewers see Lamb’s severely scarred foot. Earlier in the season, he told a story about a spy tortured in Russia whose pregnant partner was murdered during interrogation. Catherine Standish suspects the story is autobiographical, and the scars confirm it. Lamb carries deep personal trauma that he rarely acknowledges, which adds new depth to his abrasive personality.
Cartwright briefly seems on the verge of returning to the Park after saving Whelan’s life. This possibility vanishes once Lamb forces Whelan to resign. Lamb makes this move to stop the closure of Slough House, not to harm Cartwright’s prospects. With Diana now in charge, River’s chances of returning to MI5 headquarters become even slimmer. She still resents him for digging into her personal history during his early days as an agent.
The ending of season 5 prepares viewers for an intense next chapter. Despite Slough House’s vital role in stopping the terrorists, the season 6 teaser reveals that the unit has been removed from MI5’s system. Lamb and his team appear to be facing their most dangerous situation yet. With new leadership, shifting internal loyalties, and the threat of Slough House disappearing, the stage is set for a turbulent and unpredictable season 6.
