James Callis & Nick Mohammed on Getting the Call Up for 'Slow Horses' Season 5

To say that Slow Horses has an uneasy relationship with authority is an understatement worthy of an eyeroll and withering insult from Slough House commander-in-chief Jackson Lamb (Gary Oldman). 

Outside of the well-meaning but often hapless spies, Season 5 is brimming with pompous, ambitious men in suits – including returning MI5 chief Claude Whelan (James Callis), who is far more House of Lords than “M” from James Bond. However, rising terror attacks in London also affect Mayor Zafar Jaffrey (Nick Mohammed), a slick but insincere politician at risk of being ousted from office by a rival election candidate, the Nigel Farage-coded right-wing populist Dennis Gimbal (Christopher Villiers). As the spies risk life and limb, Claude and Zafar have to wield power without personal problems eating them alive; Telly Visions hopped on a couple of Zoom calls to check in with Callis and Mohammad about their Slow Horses journey.

Callis had a memorable debut in Season 4 and relished returning for one of the most confident and efficient dramas currently airing. “You have a familiarity,” he says. “I was welcomed and supported from when I arrived, but then it’s like you’ve got the badge of season four when you arrive on season five. I haven’t lived in London for a while, and doing season four was my first time back in the UK for some while, and then season five, it feels like you’re cooking with gas.”

Mohammed has been a TV comedian in the UK for years, and after netting a couple of Emmy nominations for his role as Nate in Ted Lasso, he was thrilled to join Apple TV+’s other great Brit hit. “I was such a fan of the show, even when I auditioned for it,” says Mohammed. “I think season three had [dropped], but even prior to then, I was a big fan of Mick’s books. What a treat, what a delight to be able to join such a great show. I felt very privileged.”

Fans will recall a tense scene in episode one between Jaffrey, Gimbal, and Whelan as the mayoral candidates are preparing for an election debate, where Whelan informs them that the Abbotsfield shooter was a supporter of Gimbal. Mohammed explains, it was the first scene he shared with Chris – which also involved a cameo from a famous British TV journalist.

“Krishnan Guru-Murthy is moderating, which is really fun,” says Mohammed. “I’ve done Krishnan’s podcast, so I know him a little bit, and it’s just fun to see him playing himself in something that’s about politics. Abraham [Popoola, who plays Jaffrey’s chief of staff, Tyson Bowman], phenomenal actor. We had a lot of scenes together, and he’s such a brilliant, magnetic actor; he was perfectly cast.”

Callis notes how official and immersive this scene felt. “It felt so real. I just remember when I was shaking hands with Nick, like, “Hello, Zafar.” And equally with Chris, “Oh my God, there’s Gimbal, and there’s Jaffrey.” I was totally convinced that Tyson was the security guard.”

To begin with, it seems like Whelan is having an easier time at the Park than he did in Season 4, and his initial scenes with Taverner (Kristin Scott Thomas) feel more cooperative. “Funny enough, the less antagonistic stance had a lot to do with Kristin. [I’m] so thankful. It’s just really smart. There are a lot of ways that you can play a scene. Sometimes it was looking at something like, “No, we’ve done that. Let’s take this somewhere else.” So that was a combination of Kristen and Saul Metzstein, the director. There were definitely some scenes we would start [as originally intended], and then it would come to “What if you’re trying to work together?” As you’ve seen, that’s also amusing.”

As a new character, Jaffrey isn’t as transparent as the more familiar members of the Slow Horses ensemble. He’s more moderate than Gimbal, but does he actually care about diversity and community? It’s a playfully ambiguous character in a moment where we want integrity and clarity from politicians. 

“I really think ambiguity is the right word. You don't quite know where his loyalties truly lie,” explains Mohammed. “He's obviously very self-serving, very vain. I think he probably, at one point, did care. Now he has been slightly seduced by the glamor and the power, he's obviously a little bit plastic. He cares far more about his image than enacting those policies. He’s a vain old thing. A lot of that was in the writing, but it's a really fun one to play.”

As the aftermath of Abbotsfield and the attempted assassination of Roddy Ho’s life pits Slough House against the Park, it’s easy for all these spies to miss Whelan and Jaffrey putting out fires for the sake of their image and reputation. Both actors discussed how to navigate the balance of broader comic pastiche and real, immediate drama.

“I enjoyed the challenge. But even in Ted Lasso, it became more and more layered and complicated as the seasons went on. It’s just all about trust in the writing and the direction, really. I was so well supported in both shows. But in Slow Horses, Saul as a director is phenomenal; he’s lived in that world as well, same as Will [Smith, the writer and showrunner]. It’s a joy to do something where you get to have a bit of a dance with it.”

Callis also noted he felt very supported by the direction and writing, but noted a nuance to Whelan that he feels is often missed. “Claude has a strange form of integrity, despite whatever else is going on. He is in the service because he loves his country, and he wants to serve the people in his country. And by the way, that’s not an unusual thing, if you’re in MI5 or MI6. You might get the nod because you’re particularly brilliant at university or something, but you’re doing it because you’re patriotic. This is not just a job, right?”

Slow Horses Season 5 continues with new episodes every Wednesday through the end of October. Seasons 1 through 4 are streaming on Apple TV+, and Seasons 6 and 7 are already in production. Apple TV+'s next adaptation of a Mick Heron series, Down Cemetery Road, debuts on Apple TV+ on Wednesday, October 29, 2025.