Kadiff Kirwan in Slow Horses
Kadiff Kirwan joins Slow Horses as Marcus Longridge in Series 2. Marcus brings practical experience and an appetite for action to the office, alongside habits that undermine his professional judgement. Kirwan makes him sociable and readily drawn into a dispute, particularly when Shirley Dander is nearby. Their exchanges give the team a pair who can argue about almost anything while remaining willing to back each other when the situation becomes dangerous.
Kirwan's Marcus appears across Series 2, 3 and 4. The attraction of the performance is the gap between ability and self-control. Marcus can recognise a threat and respond decisively, yet still make a poor choice when he thinks there might be money or excitement available. Kirwan avoids treating that contradiction as a joke with no consequences. The character's confidence can be funny, but it also makes the moments when he loses control more uncomfortable.
Interviews and working with the ensemble
In his 2024 TheWrap interview, Kirwan spoke warmly about Gary Oldman's generosity on set and about filming with Aimee-Ffion Edwards. He described Marcus and Shirley's bond as a platonic workplace friendship grounded in mutual respect. That distinction is useful when watching their scenes. Their insults are part of a familiar rhythm, rather than evidence that they would abandon one another at the first opportunity.
Reveal Marcus's standout Series 3 and 4 scenes
Cleaning Up and Footprints give Marcus and Shirley a sustained action partnership during the confrontation at the storage facility. Kirwan's performance works through the practical decisions of a man who has to keep moving under fire. The scenes allow his competence to become unmistakable without suggesting that his earlier recklessness has disappeared.
In Penny for Your Thoughts, Marcus's financial desperation takes a more damaging form when he sells his gun. The contrast with his field skills makes the choice painful: he understands weapons, but understanding does not protect him from compulsion. Kirwan plays somebody who can explain himself while still failing to confront the scale of the problem.
The Series 4 finale ends Marcus's story with his death during the attack on Slough House. Kirwan told TheWrap that he had known from the beginning that his work would cover three books. He praised the finished episode's emphasis on the effect of the death on the other characters, especially Shirley, and on Lamb's determination to secure support for Marcus's family. His comments place the aftermath alongside the action itself.
Television beyond Slough House
Kirwan plays Aaron in Chewing Gum, the comedy that began in 2015. Channel 4's interview with him and its announcement of the second series identify Aaron as Candice's boyfriend. It is a good earlier example of his work in an ensemble whose comedy comes from uncomfortable encounters and conflicting desires. Aaron's place in that setting differs from Marcus's working life, but both roles let Kirwan make a confident remark land badly.
The BBC's This Is Going to Hurt (2022) casts him as Julian, Adam's colleague and professional rival. The broadcaster's production description identifies that rivalry explicitly. Kirwan moves from domestic and social comedy into a hospital drama where hierarchy has immediate practical consequences. Julian's interactions with Ben Whishaw's Adam provide another version of workplace competition, with medicine replacing intelligence work and exhaustion affecting the way colleagues deal with one another.
His agency credits also include DC Wesley Ross in The Stranger and Andrew in Everyone Else Burns, which launched on Channel 4 in January 2023. Those roles extend the contrast between his police and comedy work. Rather than assuming that Marcus defines his screen persona, look at how a different institution changes the performance: the expectations of a police investigation, a religious community or a dysfunctional intelligence office create different kinds of pressure.
Stage and film
At the National Theatre in 2024, Kirwan played Cordell in Katori Hall's The Hot Wing King, directed by Roy Alexander Weise. Cordell is preparing for a cooking competition while negotiating complicated loyalties and relationships. The production puts Kirwan at the centre of a domestic ensemble, with sustained scenes that can move from teasing to conflict. Reviews singled out his leading performance, but the production's acclaim should not be confused with a personal award.
Hamilton Hodell's credits also record Sky in Guys and Dolls at Sheffield's Crucible, Daddy in Sweet Charity at the Donmar Warehouse and Nigel in the film My Policeman. These parts show musical theatre and film alongside his television work. The range is more informative than a simple list of programme titles: it includes a musical leading man, a featured comic role and a character within a period film.
Where to watch next
Choose Chewing Gum for his earlier ensemble comedy, This Is Going to Hurt for a sharper professional rivalry, The Stranger for a police role, or Everyone Else Burns for another comic community with its own rules. Each offers a different route beyond Marcus. The Hot Wing King is also an important stage credit to know, although a past theatre production should not be presented as a currently available streaming recommendation.
Questions and answers
Who plays Marcus Longridge?
Kadiff Kirwan plays Marcus Longridge in Slow Horses, joining the cast in the second series.
Who does Kadiff Kirwan play in This Is Going to Hurt?
He plays Julian, a colleague and professional rival of Ben Whishaw's Adam in the BBC drama released in 2022.
Has Kadiff Kirwan performed at the National Theatre?
Yes. He played Cordell in the National Theatre's 2024 production of The Hot Wing King, directed by Roy Alexander Weise.