Warning: This article contains major spoilers for the Season 4 finale of “Slow Horses”

The actor whose character dies in the Season 4 finale of “Slow Horses” had to keep the secret for more than a year, even from his own family. “You’re the first person I told,” he said in an emotional Zoom interview.

If you’ve already seen the finale, which is now streaming on Apple TV+, you’ll know that it’s Marcus Longridge (Kadiff Kirwan) who dies in a shootout with a hitman in Slough House.

TheWrap spoke with Kirwan about having to lie for so long to his family, friends, co-stars in the London stage production of “The Hot Wing King” and the media. During the interview, he praised lead actor Gary Oldman as “the kindest, most generous, funny guy” and Oldman’s gruff character Jackson Lamb as “the ultimate daddy bear.”

DeWrap: At what point did you find out Marcus was going to die?

Kadiff Kirwan: I knew it from the beginning. I didn’t know how he was going to die, but I knew when I signed up for the show that I was going to write three books (by the Mick Herron). I tried to make more of it, and tried not to let it kill me, but I’m so grateful. Oh man, what a death. If you go, you want to go that way, right?

What did you think about it happening off-screen?

I think this is the way they did it with the horses. There’s a kind of respect and reverence for them that I’m so grateful for. The editing we got is really special. We shot a lot around death, and I think the way they did it is incredibly tasteful, and it’s not just about his death, but how it affects everyone in the building, and everyone else, especially Shirley ( Aimee -Ffion Edwards), and how Lamb still has Marcus’ support at the end to ensure his family is taken care of.

Do you get a little choked up thinking about it?

I literally say: yes, it’s the first time I’ve said that. I didn’t tell my family that my character is dying. Sharon, you’re literally the first person I’m telling, so when the final episode comes out, I’m going to watch it with my family. I’m going to record them watching it because I haven’t told anyone since.

Wow. Marcus is also killed in the books?

It does happen in the books, yes. But what’s nice is that the way they collect material is fantastic, but they’ve been able to twist and change things in certain ways. But it made sense to have Marcus choose the evolution of the show, but also the evolution of the other people.

It’s so devastating for Shirley. They had a kind of adversarial relationship where they insulted and put each other down, but they were really committed to each other..

Complete. And it’s so rare to see a relationship in the workplace that is completely platonic, and where there is respect and reverence for each other. I love their relationship. Honestly, to this day, my scenes with Aimee-Ffion Edwards as Shirley were, and will remain, some of my happiest memories on any set.

Last season you two were killing it in the finale, taking out all the dogs, you seemed invincible. And then this one guy takes you out…

This one French assassin comes and he’s angry because the cliffhanger is obviously the way you hear the shot. You don’t know who’s gone. And honestly, I’m so upset.

Earlier in the season we had a fakeout suggesting that River (Jack Lowden) had died. So do you think this makes people think, “Oh no, Marcus can’t really be dead?”

There is no way people think (Marcus would die). My family and I made a fake video of who is going to die. We are all in this video, my brothers and sisters, my family. They all say, “Oh, it’s going to be Louisa (Rosalind Eleazar). Min is gone, so something is going to happen to her.” And I thought, “Oh god, imagine if it was Louisa,” and I just played along, knowing that I’m the one with my brain all the way down the side of the Slough House office.

You have a great poker face.

Yes. I also have a contract with Apple, and I didn’t want to piss them off. They have been very good to me, and I hope they will continue to be so in the future. It was a test for myself to keep the secret. So I’m very happy that I was able to keep it up for over a year.

That’s a long time.

I did all this press. Season 5 is obviously already in the plans, and I’m not in season 5. But even the play I did at the National Theater, I just finished it two weeks ago, throughout the play (the cast was like), “ Oh, we just saw that ‘Slow Horses’ is filming on the road.” I was like, ‘Yeah, and I’m filming all day and I have a show tonight. I don’t know where I get my energy from.” I lied to everyone except you.

I am very honored. So it’s like being a spy.

Right. They keep the secrets. It’s beautiful. And I love that there are very few TV shows that have this kind of tension and this kind of appetite. I’m just so happy to be a part of that.

In retrospect, what was Marcus’s greatest moment in the series?

Probably because of the bloody window of that store. (Laughs) I would say his final scene, the gunfight and his final scene. Because, and this is no disrespect to anyone, if he had had that conversation about dating someone like River or Ho (Christopher Chung), he might not have dated. But since it was Shirley, he went there, because there is no way he can allow anything to happen to her and the rest of the horses. So he died for the right reasons and with the right intention.

Who do you think told Marcus’ wife he was dead?

Yes, I wonder. Personally, I think it would be Standish (Saskia Reeves). I think Standish is probably the most emotionally regulated horse. She is the most equipped to deliver bad news. I think it would be too much for Shirley to do. And I think Lamb did it his own way, which was to make sure that Marcus’ family got the financial support from the agency, because he died in the line of duty, right? Oh my God, look at that. I just got a notification on my phone, on my watch, from Aimee-Ffion Edwards. She can’t stay away. (Laughs)

Everyone else has had to keep this secret too.

Every person. Oh my god, on the red carpet at the Emmys, Gary and I were doing an on-camera interview and he almost slipped and I saved it. It was so beautiful because we were both looking at each other and we couldn’t laugh, but all we wanted to do was laugh because ultimately we were there to promote season 3 for the awards they were up for. Season 4 is currently out and season 5 is in the can. So it was like, “What season are we talking about?” Luckily we didn’t get that far, but it was a lot of fun and we shared a look that will stay with me forever.

Jackson Lamb pretends to be very insensitive. And then we see that he cares in his own way.

He cares 100%. He’s like the ultimate daddy bear. He really is. He is the great protector of the secrets of the MI5 agency and the staff of Slough House. I don’t think a more fallible character has ever been written. And the playfulness that Gary pours into him is unparalleled.

It has been one of the joys of my life, not just sharing a camera and a stage with him, but developing a friendship with this man. I would honestly do anything for Gary. I think he’s just the nicest, most generous, funny guy and for someone just… you know, because when Aimee and I started, it was season 2. It’s like starting school at a new school halfway through the school year , which everyone is already sitting on. their groups, and he just welcomed us with these anecdotes and these stories, and his tongue firmly in his cheek. They don’t make them that way. They really don’t.

It’s such perfect casting.

Really and truly. We laugh a lot on set. I pray that Apple releases the bloopers at some point, because they haven’t yet. And I think if we petition, maybe they will, because there are funny, funny, funny things that we’ve done on camera that have been captured.

I was sorry to see you go. I kept hoping until the last moment that Marcus was somehow still alive, just like River.

(Laughs) I’m still trying to convince them to let me come back as a ghost or Marcus’ twin brother. It could be the first for Apple. Come on, you’re so inventive. Just let it happen.

All four seasons of “Slow Horses” are streaming on Apple TV+.