Jonathan Pryce has played kings, popes, and men who reshape the world around them, yet in Slow Horses, he turns inward as David Cartwright, a once-formidable MI5 figure now in quiet decline. There is a fragility in the way the Oscar and Emmy nominee portrays Cartwright that lingers in the smallest gestures, a performance that continues to evolve as Pryce discovers the character in real time. Five seasons in, he still approaches the role moment by moment, letting the character evolve with the audience, rather than trying to map out where it will end. “You’re playing it in real time,” he tells Gold Derby, holding onto the idea that discovery is as important for the actor as it is for the viewer.
Slow Horses, the Apple TV espionage drama created by Emmy winner Will Smith and based on the novels by Mick Herron, follows a group of disgraced MI5 agents exiled to Slough House under Oscar winner Gary Oldman’s irascible Jackson Lamb. Among them is River Cartwright, played by Emmy nominee Jack Lowden, whose relationship with his grandfather David carries a quiet emotional weight through the series.
Pryce’s Cartwright is a former intelligence figure who once knew where every secret was buried, now navigating the disorientation of dementia. The writing lets that history surface in fragments, often through the reactions of others, while Pryce shapes it through small, deliberate choices. The illness is never treated as a narrative device to be leaned on. It is approached with care, shaped by Pryce’s own experiences and the response he has seen from audiences over the years.
Below, Pryce breaks down how that instinctive approach shapes his work in Slow Horses, from the creeping physicality of David’s decline to the strange clarity that still breaks through.
Gold Derby: You’ve described Slow Horses as one of the best projects you’ve been part of. What keeps revealing itself to you five seasons in?
Jonathan Pryce: Well, it is still definitely one of the best projects I’ve been involved in, for all sorts of reasons. Mainly the scripts, which are wonderful, Will Smith and his team, and the whole production of it. It was just a joy to be involved with the various directors, and certainly the actors, Jack Lowden especially, playing my grandson.
It’s interesting because I’ve done other series, especially something like The Crown, where I know exactly what is going to happen. That storyline of Prince Philip is laid out publicly. But on Game of Thrones, I read Season 5 and established the character in a certain way, thinking he was a man intent on doing good. It wasn’t until I got the scripts for Season 6 that I realized he was a complete bastard.
Slow Horses had something of that. I didn’t read the books when I started getting the scripts, so I didn’t know the story arc David Cartwright was on. I was playing him in the moment. What the audience sees is a good relationship with his grandson, someone kindly, with wisdom to share. I wasn’t thinking that he would one day have dementia. It’s a bit like life, you play it in real time. The character grew at the same time as the audience’s recognition of him.
Talk us through approaching David’s dementia authentically.
I didn’t have any real discussions about this with the production. They took it on trust that I knew what I was doing in terms of dementia and in terms of the character. What was interesting was that Will Smith was writing in the moment as well, writing for the characters as he saw them. When we got to Season 5, a lot of things about David, how River thinks about him, were conveyed through conversations or internal thoughts like you can do in a novel. I had a conversation with Will and said it would be nice if those thoughts were made more concrete, so you saw more of River’s reaction to his grandfather’s dementia. And that happened. He wrote those scenes and elaborated them more.
In terms of responsibility, it’s the same as any character who has an illness. You don’t try to exploit it, even for sentimental reasons. It was always dealt with seriousness. There were no gags about it, other than when I really couldn’t remember my lines. I’d also had the experience of playing a character with dementia on stage in The Height of the Storm. I learned a lot from the audience’s reaction. People wrote to me or waited at the stage door to say it had been a great comfort to them. It evoked memories of their own family members. One man told me it was the first time in a year he’d been able to cry since his father died from Alzheimer’s. I knew the value of portraying David Cartwright in this way.
There was also the storyline aspect that he was a man who knew where the bodies were buried, held all the secrets of MI5 and MI6, and with dementia, would he reveal them. That was the subtext there.
There are flashes of the formidable spymaster David once was. How do those moments come through in your performance?
They were there in the script. I didn’t conjure them up. That’s what I was talking about with Will writing these moments in. You also learn about his past through Jackson Lamb, who loathes David Cartwright and knows he was a very sinister figure capable of murder. So you see it through other people. You get Shirley reacting sympathetically to him. You get Jackson knowing his history and mocking him, mocking his dementia. Elements of Cartwright’s character are revealed by how the other characters react to him.
By the finale, there’s a noticeable physical shift in David. How did you approach that decline?
I know from personal experience of family members and friends who have suffered with this disease that there’s a frailty that can come into it, partly due to vulnerability. David was getting older anyway, so he was less capable physically.
I had a brief experience in a hospital in the last few years where I felt completely vulnerable. It lasted one night, but it was frightening, that awareness you’re in someone else’s hands. I think that’s what I projected onto David, that he was suddenly in that space. Someone who has been totally in control of his life and of many other people has lost that control. You see him briefly glimpse into a room and see the other residents, and he becomes aware of what’s happening around him. When I saw it on screen, I cried a little. I thought, “Oh my God, this is so sad for this man.”
What is your collaboration like with Will Smith?
I’m not a great planner. I’m very much in the moment. It depends a lot on the other actor, how they react to the character. I didn’t sit around with Will or Saul and talk for hours about it. When you’re in a series, you kind of know where the character is going and how he reacts to situations. Will had great confidence in me, so we didn’t really need to talk a lot about it. I trusted him and respected him. The writing is so economic, which is brilliant, because it allows the audience to do a lot of work. You’re not over-explaining.
What do you most value about working with Jack Lowden in those scenes with River?
This could possibly cost me an acting award, because in the scenes with Jack, there’s no acting required! It’s a young man and an old man. It’s a young man who respects the old man, and the old man becoming very attached to his grandson, feeling he has something to give. We didn’t have to talk about the characters. When those situations exist, you understand how people behave. There’s a mutual trust, a mutual understanding, and I think a genuine fondness for each other. I like him a lot, and I respect him as an actor. I respect the way he leads his life.
You’ve played figures at the highest levels of power and also characters at the opposite end. What has that taught you about human nature?
It’s a bit like life. One day you can be in control, the next day you’re not in control. As an actor, I don’t think in terms of higher or lower. Every character has their own sense of self-importance. Sam in Brazil really knew who he was. It’s other people’s reactions that make him seem vulnerable.
With powerful people like Prince Philip, it’s how others react. You don’t have to do anything. It’s like when someone walks into a room and everyone bows. He hasn’t done anything other than be. As an actor, I like to surprise myself and surprise the audience.
