Apple TV’s Slow Horses premiered on April 1, 2022, and has now become one of the best in the genre of spy thrillers. The show follows the MI5 agents of Slough House. Washed-up agents who have failed their mission are sent to the Slough House under the leadership of Jackson Lamb, played by Gary Oldman. While they are not included in the current MI5 missions, the Slow Horses under Lamb often find themselves entangled in the ongoing missions in the show.Based on Mick Herron’s Slough House novels, the show uses numerous slang terms from real-life spies, including "Slough House." Another term that has been used in Slow Horses and revolves around the spy universe is the term ‘Joe’. The term is used for undercover MI5 agents. The Apple TV show has used the word several times to refer to MI5 agents.More on this in our story.Slow Horses: ‘Joe’ is the term used for MI5 agents View this post on Instagram Instagram PostSlow Horses has recently returned with Season 5. With a new season, the members of the Slough House have again found themselves in trouble as Roddy had shared details about his job with his new girlfriend, who happens to be working with a terrorist. This has also led the members to dangerous, life-threatening situations. But that won’t be the first time for the Slough House agents.In the preview of the upcoming episode, Lamb is seen arguing with Taverner about the danger to one of his Joes, aka his Slough House agents. This is not the first time Lamb has used the term; we have also heard him use it in Season 3. While the term might sound like a common English name, it also supports its use for an undercover MI5 agent who must appear like an ordinary person and blend in with the crowd, just like an ‘average Joe’.In Season 1, Episode 3, Lamb talks about being in Joe Country and playing by the rules of Moscow Rules. According to Herron’s novels, Joe Country refers to an MI5 agent on a field mission. Therefore, Lamb refers to being in the field for a mission. He also uses the term ‘Moscow Rules’, which refers to trying to survive behind enemy lines. Other than ‘Moscow Rules’, there is another term to be used, which is ‘London Rules’. The term "London Rules" is used to describe MI5 agents trying to survive the bureaucracy and politics. River also talks about it in Season 1 and says:“Moscow Rules, Watch Your Back. London Rules, Cover Your A*se.”Over the years, we have come across numerous slang terms used in the real world by MI5 agents, Joe, Moscow, and London Rules, among others. Another famous slang term used is ‘Dogs’, which agents, especially Lamb, use for the internal tactical unit of MI5, currently led by Emma Flyte and previously headed by Nick Duffy.Along with Gary Oldman, Slow Horses also stars Jack Lowden, Jonathan Pryce, Kristin Scott Thomas, Saskia Reeves, Christopher Chung, and Aimee-Ffion Edwards, among several others.Keep reading Soap Central for more such stories.Also Read: The final scene from Monsters: The Ed Gein Story mirrors a chilling scene from Ryan Murphy’s AHS: Hotel