‘Slow Horses’ Showrunner Breaks Down Season 4’s Finale Death And Teases Season 5: “It Has A Different Feel”

Three weeks after (the other) Will Smith won his first Emmy award for Slow Horses , the writer, executive producer, and showrunner sat down with Decider to gush over his critically acclaimed Apple TV+ drama, unpack Season 4’s most memorable moments, and break down that heartbreaking finale death .

The latest installment of the beloved espionage thriller, based on Mick Herron’s Slough House book series , followed Jackson Lamb (Gary Oldman) and our favorite misfit MI5 agents River (Jack Lowden), Louisa (Rosalind Eleazar), Ho (Christopher Chung), Shirley (Aimee-Ffion Edwards), Marcus (Kadiff Kirwan), Standish (Saskia Reeves), and new addition J.K. Coe (Tom Brooke) as they raced to investigate a bombing, the attempted murder of David Cartwright (Jonathan Pryce), and mysterious new antagonist Frank Harkness (Hugo Weaving).

In an unexpected twist (for those unfamiliar with the books), the high-stakes season packed with Slow Horse s’ signature brand of action, humor, and whip-smart spy shenanigans, culminated in the emotional loss of a beloved Slough House fixture: Marcus Longridge .

“It’s really sad. You never want any of these people to go,” Smith said over Zoom, rattling off several of Slow Horses ‘ past deaths, including Min Harper and Spider. “Kadiff was great and said, ‘This a good way to go. It’s impactful.’ But it’s very hard.”

On top of the heroic nature of Marcus’ demise, those mourning Slough House’s resident gambler can take comfort in the fact that his death will have a powerful impact on the story moving forward. “The great thing about Marcus dying, in dramatic terms, is not just that you miss the character, it’s the impact,” Smith explained. “The same with Min and what that did to Louisa. Marcus’ death will devastate Shirley, who never really opened up or got close to anyone in a way that we’ve seen before. She’s just going to be ripped apart from him.”

For more behind-the-scenes insight into Marcus’ death , the Season 4 finale , what to expect from Slow Horses Season 5, and more, Decider’s full interview with showrunner Will Smith awaits.

As always, Season 4 was superb. We met quite a few new characters, but I’d love to start by discussing how amazing Hugo Weaving was as Frank Harkness, a.k.a Dad. All of his scenes — especially the ones with Jack in the finale — were so stellar. What was it like watching him fit so seamlessly into this world?

Well it was a total dream come true, because I’m actually related to him. He’s my mum’s cousin. And so I’d been out to stay with his family in Australia, and then he came to my wedding, because he was filming and there were family coming over. So we sort of cross paths every five, ten years. But I’ve always completely idolized him because he’s the famous, brilliant actor cousin of my mom’s. And then when it came to casting this, James Callis for Claude, Joanna Scanlan for Moira, and Hugo for Frank were my three. That’s who I had in my head. And we were able to get them all. I just thought that with Hugo, there was just enough of a similarity in looks to Jack that it would make sense when you reveal it, but it wouldn’t tip you off. And he’s just an amazing actor. I just thought he’d bring the power and malevolence and rawness of Frank that you want. It was wonderful to watch. I’m so lucky. I just I can’t believe all of this has happened.

Another fresh face I hope to see more of as Tom Brooke. J.K. Coe really stepped things up in the finale with the tea water, and comforting Shirley, and that kill shot. What’s his induction to Slough House been like?

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He just went straight in. Tom, I just adore beyond any words I can say. He’s an incredible actor and so thoughtful. There’s such detail in what he does. The line he does where he’s unlocking Ho’s handcuffs, and Ho says, “What happened when you were handcuffed?” And he says, “A man threatened to cut open my stomach with an electric carving knife.” He’s telling the story and he knows the words, but all the emotion is gone from it. It’s throwaway. And I thought it was just such an incredible delivery that said so much about that character. That’s what Tom does — so much with so little. When it came to casting that part, he doesn’t say a lot across it. A lot of time he’s got headphones on, miming his piano playing. And so you had to have an actor who would be able to have the confidence and the ability to be in the back of a scene, but still have a presence. Tom does all of that and more, to the point where a lot of Tom’s notes when we discuss scripts — particularly in Series 5 — he’s got a whole trajectory worked out where he’s like, “Can I say less?” And usually the opposite is true. I just love it. I just think it’s such a specific part, such a hard thing to cast. And he is that character.

We also said goodbye to several more characters this season. We obviously have to talk about Marcus, who I loved. As hard as it is for viewers and characters to say goodbye to a main Slough House fixture, I imagine it’s incredibly tough for the cast and the crew. How sad was Kadiff’s send-off for you all?

It’s really sad. Everyone loved Kadiff, just like they loved Min and they loved Freddie. You never want any of these people to go. But Kadiff was great and said, “This a good way to go. It’s impactful.” And also, amazingly, he has not told anyone. His friends and family don’t know that he’s going, to the point where he’s told them he’s filming Series 5. He’s been like, “I was filming today,” and then he’s going to go watch it with his family and they don’t know what’s going to happen. I would love to watch that and see how they react. [Laughs] ( Note: Be sure to read Decider’s interview with Kadiff Kirwan for his side of the story .)

But it’s very hard. The great thing about Marcus dying, in dramatic terms, is not just that you miss the character, it’s the impact. The same with Min and what that did to Louisa. Marcus’ death will devastate Shirley, who never really opened up or got close to anyone in a way that we’ve seen before. She’s just going to be ripped apart from him. Kadiff and Aimee both said what they love about their characters is it’s quite unusual to see a male/female friendship and it’s just a friendship. There’s no hint of romance. That’s just not what it is. They haven’t really felt like they played that before or had seen that before. So doing that and then killing, it’s powerful. It has an impact. And when I watch TV, I want to feel stuff and react and be emotionally moved by things.

When you and I spoke ahead of Season 3’s finale , we discussed one my favorite scenes where River hugs Louisa in the car, and you revealed that was Jack Lowden improv. Is there a Season 4 scene you want to shout out, either because of improv or that really stands out in your mind?

I’m just go start listing all of them. [Laughs] I think River in Louisa in the pub. Again, they’re so special. What those actors do with that. It’s sort of romantic and flirty, but not. And sort of like a brother/sister [dynamic]. Obviously there was the confusion in that particular scene in the pub where you thinks he’s gonna ask her out and doesn’t ask her out. I love that. And then the scene with Jonathan and Jack in the bathroom I thought was incredible. Gary and Saskia were amazing, when he goes to her flat and Saskia there is acting as Catherine acting for Lamb, trying to pretend that she doesn’t know that River was there. Gary finding Sam’s body — no words, but just it’s Gary, so it’s just the most incredibly powerful scene. We’ve only ever seen Lamb be nice to Sam Chapman and Molly, and now Sam’s dead. Again, it’s that subtracting the loss that all these characters go through. And then Jonathan and Jack in the care home — I knew that would be amazing, because it’s Jonathan and Jack and they’re amazing. I knew that was going to be horrendous in a good way.

Those were incredible standouts, and I love that you didn’t mention two of the most popular scenes I’ve seen on social media. One was when Lamb saves the day in that car in Episode 3, and that same episode we see River’s great escape where he falls through the roof and runs away from those men and the dog. No one on TV runs better than Jack Lowden.

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[Laughs] I know. He’s so great physically. And it’s funny, that tin roof bit, I realized after that that’s my mini tribute to Oliver Hardy. It’s a very Laurel and Hardy kind of “I’ve won, screw you, bang!” There’s a lot of influences swirling around there.

When we spoke last did you ask me about The Thick of It lines that were in Slow Horses — about Norway?

Yes! The “explaining Norway to a dog” line.

It’s been bugging me for a year, so I’m really glad I get to finish this off. I was thinking back afterwards and I forgot that was a The Thick of It line. [Laughs] I’m so glad it’s you because I spent a year being like ‘My god, I could have said that.’ I remembered it as a line from my standup, and so I put it in thinking, “Well, no one’s going to remember that.” And I think I’ve said it on a radio panel show. So I put it in and I was like, “People think it’s The Thick of It reference? No, it isn’t.” And then I had to ask one of the writers, “Do we have that in the show?” And he was like, “Yeah, you put that in the show.” And I was like, “God. This is The Thick of It reference.” [Laughs]

Oh I love that you forgot. The fans definitely didn’t — they know it and love it.

[Laughs] I know. It’s so funny, that line comes up a lot.

Going back to the the finale, every performance from Jonathan Pryce is so astonishing. But that final goodbye between him and Jack in the care home that you mentioned and his whole battle with dementia gutted me. At the same time, he also made me laugh so hard in the finale when Ho wanted him to sit on Lamb’s toilet and he was like, “No, I’m good.”

I know. It’s just great that we can find those moments within the show to have those kind of throwaway jokes. That’s what I love. You’ve got that big shootout and you’re like, “My god, it’s Catherine and Moira defending him. Ho is hidden away and is being of no use. And these are the two least equipped people in the building to protect Jonathan and then they get a gun but drop the bullet.” It’s funny, but it also adds to the stakes and the tension. The care home scene is one of the things I’m proudest of. I find it very moving, and not the sort of thing you see in these kind of shows, so it feels different and exciting to kind of do something like that.

We’ve talked about everything from Coldplay to the score and the iconic theme song. Slow Horses makes such amazing use of music, so I wanted to ask about the ending Nick Drake song that plays while Lamb and River sit at the bar.

That was that was Adam Randall’s choice, the director. He put that in and I saw I was like, “That’s perfect. It’s just beautiful.” Every time I get very melancholic when it comes on. It’s a sad season. The series is about loss, and loneliness, and people trying to find their place and their way in the world, and ending on that moment with Lamb and River not being together all season. At the end of it, River’s kind of lost his grandfather in many ways; the image he had of his grandfather. He’s found his father and he turns out to be a monster. And the only father figure he’s left with is Lamb, who called him to the pub because he wants some expenses signed off and then says, “Will you stay for a drink? If you buy your own and don’t say a word.” That’s as good as it gets. And that was just a brilliant, brilliant choice of music by Adam. I love what he did with that.

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I’m in desperate need of Season 5. What can you tease for us and when can we expect more?

I honestly don’t know when it’ll be out, but I can’t imagine that Apple would want to have it be later than when Series 4 went out. I can say that Roddy Ho comes to the fore shall we say. And part of what that involves is set up in Series 4. So there’s a little thing that happens that is connected to the main plot of Series 5. Obviously with with Ho at the center it has a different feel to Series 4, which is a much more brutal and emotionally raw season. There’s still bad stuff happening, obviously. But you’ve got Ho. So it’s a it’s a bit more Ho next time, and more Coe. Coe starts to speak more which is nice.

Last time we spoke you said you’d be open to making the series as long as Gary Oldman, and Apple, and fans wanted more, and three seasons in the show just won its first Emmy. Congratulations on that. Your “I come in peace” joke slapped. [Laughs] How did it feel to finally get that recognition from the Television Academy?

Honestly, I never felt we were overlooked or that we were owed anything. But it’s tremendous. It’s such a cliche. It just felt like there was a lot of love and support in the room for the show, which was lovely. And some other people who were collecting statues that night sent me very lovely messages about how much they love the show, which means the world to me. To have praise from my peers means so much. You say, “My god, really? If you like it, it must be all right.” So it felt fantastic. It was great for the show. And it’s great to get an award, but you also hope this means more people watch it, because I’ve done my silly joke and it’s on TikTok apparently.

You’re having quite the year, because you’ve also won Emmys for Veep , which has had a real online resurgence ahead of the 2024 election. What’s that been like to behold?

It’s kind of crazy. I can’t remember what the viewing was but it leapt 500% or something crazy. It’s fantastic, because I’m very proud of that show and everything we did on that show. That was another incredible cast and a wonderful experience. It’s getting a new generation of fans.

Before we go I wanted to ask your thoughts on the Slow (Pommel) Horse promo that Apple TV+ posted with Olympic icon Stephen Nedoroscik.

[Laughs] Yeah that’s pretty mad. I didn’t know anything about it, and I was like, “Oh my god, it’s everything. I’m not sure how much crossover there is, but —

So he’s not going to be on the show?

No, he’s not guest starring. [Laughs]

Slow Horses Season 4 is now streaming on Apple TV+. Read on for everything we know about Slow Horses Season 5 .

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