English film director Simon West has been making movies for nearly three decades, but “Old Guy,” an action comedy that stars Christoph Waltz, Lucy Liu and Cooper Hoffman, might be his most enjoyable production yet.

“It’s very relaxing for me to work with people of that level,” West says of the cast. “Because it looks effortless, but, you know, it’s years of experience and skill gone into it.

“So it’s a pleasure to watch, but also a pleasure to be a part of because I’m not carrying so much of the weight,” he says. “I’m not having to put on this huge roller coaster ride that is all based on my puppet mastery. I’ve got actors that are gonna take a great script and run with it, and I just need to make sure that they have everything they need to do that.”

West, who made his debut with the over-the-top 1997 Nicolas Cage action movie “Con Air,” has also mined that genre with stars and films including Angelina Jolie in “Lara Croft: Tomb Raider,” Jason Statham in “The Mechanic” and Sylvester Stallone with a host of action heroes in “Expendables 2.”

Before that, he worked in music videos, including the iconic Rick Astley clip for “Never Gonna Give You Up.”

But on a recent phone call with Liu to talk about “Old Guy,” West says he’s seldom been able to simply sit back and view his work as audiences do.

“That’s what I loved about this film,” he says. “It’s a pure pleasure to watch as well. It’s one of the few films I’ve made that I can watch over and over, because it’s more about the actors than it is about me.

“I can watch it as a film fan and as an audience member, rather than, ‘Oh my God, I messed that up. I should have done that better.’ Or, ‘Why didn’t I do that?’ ”

“Old Guy” premiered at the Newport Beach Film Festival in November, which honored Waltz, an Oscar winner for best supporting actor in “Inglorious Basterds,” with its Icon Award.

Waltz plays Danny Dolinski, an aging hit man for a London mob who, after an injury to his gun hand, is demoted to training his younger replacement, Wilhborg, played by Hoffman. With Dolinski’s longtime friend Anata, Liu’s lovelorn manager of a high-end London brothel, they head for Belfast, Northern Ireland, on a job that quickly spirals out of control.

In an interview edited for length and clarity, West and Liu talked about what drew them to the project, how the character-based approach to action filmmaking made “Old Guy” a bit different for that genre, what it was like working with the veteran Oscar winner Waltz and relative newcomer Hoffman, and more.

Q: Let’s start with your initial attraction to the screenplay and characters.

Liu: Well, I have to say I loved how colorful the character was. I also am a big fan of Christoph and Simon and I really enjoyed working with Cooper. I’ve seen his work before (Paul Thomas Anderson’s “Licorice Pizza” is among his films) and I think he’s just really spontaneous and fresh as an actor. So that kind of trifecta was really the reason to jump on board.

West: I loved the idea because I just love the three characters. It’s a very contained film because it’s really about the three characters. And even though it’s in a world of, ostensibly, hit men and seedy underlife, they could be doing any jobs.

Lucy’s character is running a club of ill repute, but she’s just the manager. I think in the film, when she describes what she does, she says she problem-solves and manages people. It just happens to be in a sort of criminal and illicit world. And in this way, too, for the other two guys. They’re hit men but they could be plumbers or electricians, and they’re just two different generations not getting on.

I think that was what attracted Christoph as well. He would always talk about that, saying it’s about the relationship between these people, and they just happen to have, in our world, bizarre and exotic jobs of hit man and running dodgy clubs. It’s just an interesting three-way relationship and that’s what attracted all of us, I think, to it.

Q: Lucy, I think most of your scenes in the film are with Christoph. Tell me what it was like working with him as the characters come to the realization they do by the end of it.

Liu: I think that we had a very immediate connection. He’s very easy to work with and he really had a great sense of where his character came from. So because we were old friends in the movie, I think there was a really natural chemistry between us that I appreciated.

He’s also somebody who really connects to what he’s doing, and he’s very present. If something doesn’t make sense, he, and Simon knows, he’ll say, “This isn’t making sense to me. Why are we doing this?” That’s somebody who’s a problem solver and also very solution-oriented in getting to where he needs to get, or where we all need to get in a scene.

Q: And as things get worse in Belfast, their relationship deepens.

Liu: He brings a lot of value to how that kind of came about. You know, even when Anata’s going through her kind of dark period, the way that he approaches her, the dynamic between them is she doesn’t really take him that seriously. But then something happens in their friendship that sort of changes the way that she sees him and sees his honesty.

He’s always been kind of this guy that she’s known, but it’s never been this deep. We didn’t really over-rehearse. We just kind of mapped out the location, where we were gonna end up fitting, and you really felt his support in wherever and however it was going.

Q: The film has great action scenes and shoot-outs and things that are part of a hit man’s job, but there’s a heart to it as well. Simon, how does that kind of material add to the action genre of it?

West: Well, I mean, that’s why I wanted to do it. Because I’ve done more action than anyone deserves to do. So I was attracted to this because it was so character-based that it was, you know, a day off for me in some ways, because the actors, Lucy and Christoph, are at the height of their powers and their skills.

All I’ve got to do is make sure they have an environment that lets them do their best work because they’re certainly going to do great work if they have that environment. It’s more watching them do their great performances and their interaction. And the chemistry, thank goodness, worked really well. When they’re looking into each other’s eyes, it’s real. And I’m sucked into the story and the characters.

Q: Lucy, you’ve got action movies like “Charlie’s Angels” and “Kill Bill” on your resume, but you don’t get to kick people’s butts here like in those movies. What’s it like not to get into all that?

Liu: I mean, it was really a relief not to do it, honestly. (Laughs.) For me, the beauty of it is that she’s a bit of a third wheel in this, and she comes along for the ride, literally. You know, I never planned to be in action when I started out as an actress. I fell into it. And I guess there was something about it that people really love.

I was always a big fan of action movies myself, but there’s a lot required for somebody who wasn’t born into that and didn’t grow up doing that. So the pressure was off for me.

When I watched the movie, what I love is it’s kind of an old-time action movie. The expectations of what we’ve so often witnessed in all of the other movies that are the green screen, the blue screen — we’re creating another world. We’re world-building. In that sense, it seems like a much smaller movie, something that was done decades ago, and I enjoyed that because you can really focus on the characters and their story, and their connections or their disconnections.

I liked that Anata was willing to put herself out there. She could have just taken off, but she obviously cares for her friends and put herself in danger, even though she really doesn’t know what she’s doing. That’s the key element for me.