It’s fair to say that when audiences see River Cartwright at the beginning of Apple TV’s “Slow Horses” Season 5, he is not in a good place. The previous season revealed that River’s father, Frank Harkness (Hugo Weaving), is both a sociopath and the leader of a network of trained assassins. It was also revealed that Frank had fathered numerous sons and raised them to carry out his hits.
“I think for anybody, that would be quite traumatic,” says Jack Lowden of his character River’s damage, which carries into Season 5; his base of operations, MI5’s Slough House headed by Gary Oldman’s Jackson Lamb, has become a bit too much for him.
“When I was filming that season and Season 6, my grandfather is at the forefront of my mind. I feel like that begins to overtake his ambition because he wants to make his grandfather proud,” says Lowden. “He’s not in the best of head space, and he’s thinner physically. I think nerves-wise, he’s thinner. I don’t think he’s particularly in a happy place or particularly well, so to speak.”
Lowden details peeling back the layers of River and why the character ends up in a much more hopeful place as the show heads into its sixth season.
Let’s get right to it. In Episode 5, “Circus,” River is lying to Jackson about the death of politician Dennis Gimball (Christopher Villiers). Take us into his mind. Why does he lie?
What I’ve always found interesting about River is his pride, because I find pride in people incredibly petty, and it pushes people to do stupid things for the sake of how they look or how they come across. He’s trying not to look bad. This season, he’s not in a great head space. I love the fact that, no matter that his personal life is falling apart, at the end of the day, at work, he still doesn’t want to look stupid.
You’ve said River’s grandfather, played so brilliantly by Jonathan Pryce, impacts a big part of his actions. What were those garden scenes like when they have a heart-to-heart?
Jonathan and I talk about that quite a lot — losing someone is horrific, and the grief is terrible. But you are watching someone in front of you disappear slowly, with the terrible disease of Alzheimer’s or dementia. I’ve not experienced it yet, but I can imagine it’s horrific. On top of that, his grandfather is his hero. He’s also trying to emulate his grandfather and follow in his footsteps, and to watch him evaporate in front of him is terrible. But in true “Slow Horses” fashion, David will still give him a little seed of something that will sort of open up the entire thing for him. I took that as a real moment of hope. I think, in the moment, River is very much focused on the problem at hand. But when you get someone who has
that condition, and there are these little kernels of hope that they are still who they were — it’s just so moving. I think I actually found that a hopeful scene. But again, playing with somebody like Jonathan Pryce, I would be lying if I said I completely stayed in River’s head space.
How do you prepare for something that’s so heavy for this character?
I tend to stay away from those moments as much as possible. I try to come at them from as jolly and playful a place as I can, because I think that’s true to what happens in life. When you’re faced with grief, sadness or tragedy, you’re trying really hard not to give in to the terribleness of the situation. So I tried to
do that with these scenes. I don’t spend the night before pushing myself into a certain state. The challenge of just instantly trying to put yourself in that situation and using your imagination — at the end of the day, that’s what I feel makes it fun.

By the end of the season, River thinks that he’s finally got his ticket out of Slough House. Instead, Lamb makes sure River stays at Slough House. Where would you say River is at the end of the season?
As far as he’s concerned, he’s pulled off a lot of impressive feats. In particular, the saving of James Callis’ character was meant to give River that moment of feeling like he’s earned his place, gotten his stripes back, and just needs to go to Lamb. He has the chance for a promotion and lays it at the door of what
is probably the worst boss in history. River and Lamb are intrinsically linked, but they’re often kept apart, which makes their interactions more special when they do happen. There’s more respect for Lamb now, but I do think we leave River in a more hopeful place than where he was at the beginning of the season. I’m glad about that because, during this season in particular, he’s not exactly a happy bunny.
What has it been like peeling back the layers of this character over the seasons?
It’s an interesting question, because this is the only experience I’ve had doing anything recurring for this long. I find it incredibly hard, whenever I do watch the show, to differentiate myself from River because I’m also watching a guy who was 29, I think, when I began. I’m now 36, and the world has been through a lot in that time. Everybody has. I find it quite interesting to just watch someone growing up — not just River, but myself. I think what I’ve enjoyed is seeing myself grow up as an actor as well. It’s why I still act. It’s not necessarily because I want to play all the great characters — though, of course, there are people I want to work with and still haven’t worked with. But I go to work every day because I want to get better at what I do. I feel incredibly lucky as an actor that this is a profession you can learn to master, even though you probably never will. I can see my progression. I remember how I was feeling on a certain day. I remember the difference in how it felt in Season 1 compared to Season 5. I just see a boy who’s sort of eventually becoming a man. Hopefully.
Who are some of those actors you’d like to work with? Let’s manifest.
Matthew Macfadyen; he’s a benchmark for me. I find his range remarkable. I think he’s phenomenal, and I would desperately love to work with him. Last year, I was very fortunate to work with Martin Freeman. He is another actor that I think has incredible range and has a severely sharp technical ability that I got to see up close night after night.

