Fans of fantasy films likely know Ben Barnes best from his recurring role as Prince Caspian in the Narnia series. (He also played the title character in 2009’s Dorian Gray.) However, in By the Gun—a new crime thriller set and largely filmed in Boston, and written by Reading-bred writer/producer Emilio Mauro—the 33-year-old British actor is taking on a very different role. Barnes plays Nick Tortano, a tough kid from Boston who dreams of being a made man. Barnes’ tattooed, leather-jacketed Nick, with his slicked-back hair and impressively authentic Bahston accent, is a far cry from a foppish prince, but the actor brings a tenderness to the role of the conflicted would-be gangster, who finds that a life of crime isn’t all it’s cracked up to be. We got Barnes on the line from L.A. to talk about his transformation, hanging with Boston rapper and co-star Slaine, and his favorite North End spots before By the Gun (also starring Harvey Keitel and Leighton Meester) premieres in Boston on Dec. 1.

This role was a big departure from previous parts, like, say, Prince Caspian. What drew you to the role? You almost answered the question in the question. A lot of my thought process behind this particular role was that it was so different from everything I’ve done. It’s been six years since I filmed the last Narnia film that I ended up involved with, and I feel I’ve done a lot of growing up in that time, as men tend to do—you know, we’re trying to catch up with the women in terms of growing up. And I think part of the joy of acting, for me, is being able to take on different types of characters and trying to see the world through their eyes, immersing yourself in their world. And this character particularly, in terms of being immersed in a different world, was very exciting to me, because the cast is filled with a lot of different local Boston actors, the writer was from Boston, and it was very, very important to be involved with it. I could tell when I spoke with the director on the phone, before I took the part, it was very important to them for it to feel authentic to the sort of underground world of Boston. And so that was something I was really keen to experiment with.

The other logistical thing was that I had seen a film that the director, James Mottern, had made called Trucker, which I thought was really interesting. It was really good characterization in terms of a singular character. Michelle Monaghan played a trucker, a female trucker, and it was just about her and her psyche, her thought process navigating through the story. You really felt like you were in her head. And I thought this was the same kind of story, but with guns and gangsters instead of trucks. Because it’s kind of focusing on one guy’s tensions and dilemmas and ups and downs through the journey.

What kind of research did you do before getting into the character of this conflicted guy? I had about two or three weeks before we started filming, so I flew straight out to Providence, which is where we shot three quarters of the film. We shot the remaining stuff in the North End of Boston, which was awesome. Actually me saying it was awesome is actually sort of part of it, because, like I was saying about the other people in the cast who were from Boston, this guy called Damien [DiPaola] who played one of the Italian restaurateurs and shopkeepers, who is a fine actor but also an Italian shopkeeper and restaurateur in the North End. And we went to eat at his restaurant [Carmelina’s] a couple of times, which was just incredible. So that was sort of the first thought, just sort of walking around Boston’s North End, just sort of breathing in and out, and feeling like you belong there. And then I said, look, I want to meet some of the more shadowy types. So Emilio [Mauro], the writer, kind of organized a go-to of a particular bar and a particular restaurant on a particular night, and we’d shake hands with particular people who didn’t really talk to us, giving us sort of insight into the Boston underworld. It was very interesting to watch their behaviors with each other. It’s little things, like the way they greet each other in terms of the handshakes, and the hand cupped on the back of the neck, or the way that they kiss or hug, and the way that they kind of strong-arm each other in conversation—that kind of thing is something that’s really, really useful to just immerse yourself in. I wouldn’t necessarily describe myself as a method actor in terms of trying to actually accomplish being that thing, but I definitely have sort of a very immersive technique. I want to be around it like a sponge, and I want to feel like I’m in it. And I feel like this was the most that I’ve ever felt that way about something.

In the weeks leading up to this, I think there were changes in me as a person. When I arrived in Providence, I had longer, floppier hair, and a sort of scruffy beard. I went into a store to get a drink, and there was sort of this gang of older teenagers by the front desk, and I went up to buy my drink. I said, ‘Excuse me, just a moment boys.’ And they’re like ‘What?’ And I was just kind [puts on a timid voice] ‘Um… can I buy this drink?’ And they were sort of grunting and not moving. Then about three weeks later, we were in the middle of the shoot and I had on my costume—I had cut my hair and shaved my beard, and I had this fake tattoo on my neck, and I was walking and talking with the accent I had been speaking in for the last few weeks. And I went into the store and the same group of kids was in the store. And I just grabbed what I wanted to buy and walked up to the desk, and I was like [puts on tough guy Boston accent] ‘Excuse me,’ and then they turned around and looked at me and gave me the up and down, and then just moved out of my way. And I’m not saying that because I’m trying to show off how much it was working or anything, but just that was the psychological exercise I was employing in terms of my characterization, and it was making an impact in the real world, which to me was really exciting and interesting.

Was that empowering, feeling like a tough guy out in the real world? It was really empowering. It made me really want to just, like, hit the gym seven days a week and get tattoos on my face and neck. [Laughs] But unfortunately I’m just really not that kind of person in real life. I think we all have different levels and different ways of being tough. And I have to find different ways of being tough. If I throw a chair and start screaming, it’s going to be laughable, whereas some actors find that the easiest thing in the world.  I might be misquoting, but there was something by Tom Hardy once—who I think is really brilliant—he was saying, ‘It’s the easiest thing for me in the world to scream and throw a chair. But if I had to sit down in front of someone and tell them I love them, I find it really difficult.’ And for me, it’s the opposite. I think that’s why it’s taken me so long to play a tougher character like this, because I have to find different ways to be intimidating, with stillness and sort of a lack of reaction. There’s so many different ways to be tough. There’s so many different ways to be tender.

Did you sympathize with Nick as a character? I honestly think that if your job is to play a particular character, no matter if you’re playing a terrorist or what, your job is to empathize with him and support him in all the decisions that he makes, and be happy with those choices. That’s just 100 percent what you have to do in order to make him a believable person. Because that character believes what they’re doing is right. Even if they’re blowing people up, you have to find a way to make that reasonable to you. But having said, that—and we actually shot this but it didn’t make the final cut—after I kill someone for the first time, we actually shot in scene I suggested that we add in, which was a scene of Slaine in the car wash, hosing the blood off his shoes and burying the body, and Nick is leaning against the wall of the car wash literally throwing up. Just vomiting. And then he sort of washes away the vomit with the same hose. In the heightened-reality gangster films, it doesn’t really mean anything to off somebody. [But] If they’re real people who have seen these movies who would react like real people to killing somebody, and I wanted to take this journey with Nick—if he did something that he saw as beyond the pale, or crossing the line, then I wanted him to have a real human reaction to it, no matter how vulnerable that was.

The Boston accent isn’t always done well in movies, how did you get it down, especially with your British accent? Honestly, the rest of the cast just wouldn’t let me get away with it—they would jump on me if a word sounded strange to them. Slaine would literally slap me in the face if he wasn’t convinced by what was happening. He was so suspicious of me at first. He was looking at me like, who do you think you are coming into my ’hood and pretending to be one of us? Like, go away. He literally looked at me like that when I turned up, and I thought, ‘This is going to be really difficult.’ And literally, within days he’d kind of seen what I was bringing to the table, and why I was there, and I think then something sort of clicked between us. He’s thinking I’m a drippy British actor type, and I’m thinking he’s a scary Boston rapper, he’s not really an actor, and then he realized that I was going to pour my blood and guts into this to make it feel authentic. And I realized he was actually probably one of the most talented, naturally gifted actors I’ve ever met in my life. So we very quickly sized each other up, and then we had this very kind of fun, rough-and-tumble relationship, where we would kind of go on this buddy journey together, which was so rewarding.

That was going to be my next question: Did Slaine take you out to any of his favorite local spots? Yeah, he took me to, like, weird underground cigar bars—even though I smoked a cigar once and it made me sick—and he took me to various bars and restaurants and stuff. I actually can’t wait for December when I get back to Boston and we have the premiere screening, so we can do it again, because it was really fun.

Any favorite places you visited while you were in Boston? I’m trying to remember the name of this restaurant because it was so, so good. I even emailed it to somebody recently because they were going to Boston and I was like you have to go to this place. [pauses] I’m sorry, I’m just loading an email so I can remember the name of the restaurant I went to because it was amazing. God, I need a new phone. Here we go—Carmelina’s!

I know that place. So I assume you’re going to go back when you’re back in town? I hope so! I’m only going to be there a couple of nights, because I have another few projects coming out so I’m sort of running around doing publicity for all of them at the moment. … I won’t tell you everything I’m doing, but I just did a mini-series set in Boston, called Sons of Liberty. I play Samuel Adams. It’s on the History Channel at the end of January, and it’s actually badass. It’s a three-part mini-series about the buildup to the American Revolution, and it’s really cool.

We’ll make a local of you yet. Yeah, exactly. Actually, I really do think that Boston, for me—I actually did another film there before (which never came out, because it wasn’t very good [laughs])—but it’s the only place in America I’ve visited that reminds me of London. Just the way that the park is sort of set in the middle of the city, but not in a Central Park kind of way. It’s got lots of different cultural areas to it, and just the way that the people are, as well—kind of warm, but individual. It’s not like London, but it’s the most like London that I’ve found in America so far .