Marcus Longridge is a British MI5 agent who finds himself stationed at Slough House; a place often associated with misfit agents. He is portrayed by Kadiff Kirwan in Seasons 2, 3, and 4 of Slow Horses. Longridge’s character is marked by a tumultuous past, particularly his struggles with a severe gambling addiction that led to his reassignment. Despite his challenges, he is a skilled operative, known for his tactical expertise in weapons and combat, making him a formidable presence in the world of espionage.

Trivia/Facts

• Marcus Longridge is a British MI5 agent who works at Slough House. He is portrayed by actor Kadiff Kirwan in Seasons 2, 3, and 4 of the series. Longridge is known for his complicated past and struggles with personal issues. His character brings depth to the storyline as he navigates his life as a spy.
• Before being assigned to Slough House, Marcus worked in tactical operations at the MI5 headquarters in Regent’s Park. He had a promising career but faced challenges due to a severe gambling addiction. This addiction led to his reassignment, showcasing the flaws even in skilled agents. Despite his past, he remains a competent operative with valuable experience.

Tom Brooke, Christopher Chung, Aimee-Ffion Edwards, Kadiff Kirwan, and Rosalind Eleazar in Grave Danger (2024)

• Marcus is highly skilled in weapons handling and hand-to-hand combat. His expertise almost earned him a place in a specialized group known as The Dogs. However, he chose not to join them because he did not want to work under Nick Duffy. This decision reflects his desire for independence and moral considerations in his work.
• Longridge is married to Cassie Longridge and has two young children. His family is an important aspect of his life, adding complexity to his character. Balancing his family responsibilities with his work in MI5 is a recurring theme in the series. His love for his family drives many of his decisions, both personal and professional.
• Due to his background in tactical operations, Marcus possesses two Heckler & Koch MP5K submachine guns. These weapons are likely illegal and kept locked in the boot of his car. This detail highlights the risks he takes as a spy and the challenges of living a dual life. It also adds to the tension and danger surrounding his character in the series.

Kadiff Kirwan and Rosalind Eleazar in Drinking Games (2022)

Marcus Longridge’s Relationship with Other Characters

• Cassie Longridge: Marcus is married to Cassie Longridge. They have two young children, and his family is very important to him. His job and gambling problems sometimes create tension in their marriage. Despite these challenges, he tries hard to be a good husband and father.
• Nick Duffy: Marcus has a complicated relationship with Nick Duffy, a key figure in MI5. He almost joined Duffy’s elite group called The Dogs but decided not to, showing he doesn’t fully trust Duffy. This choice highlights Marcus’s desire to keep his independence. Their interactions often reveal a struggle between loyalty and personal beliefs.
• Colleagues at Slough House: At Slough House, Marcus works with various misfit agents. They share similar struggles and often support each other. He sometimes takes on a leadership role, helping his colleagues through tough times. These relationships add to the themes of friendship and teamwork in the story.
• Former Tactical Team Members: Marcus keeps connections with his old colleagues from the MI5 headquarters. These relationships are usually professional, but they share a bond from their past experiences. His skills make him respected among them, even if he feels out of place at Slough House. This contrast between his past and present makes his character more interesting.
• Mentorship and Rivalry: In MI5, Marcus faces both mentorship and rivalry. Some younger agents look up to him for advice, while others see him as competition. He must prove himself despite his past issues. This mix of relationships creates tension and adds depth to his story.