Coming to terms with who you are and what you have is an inevitable part of any young actor’s process of maturing in Hollywood. But Jamie Campbell Bower seems to have found the perfect role to explore that on screen, playing Jace in The Mortal Instruments: City of Bones. A sarcastic, expert killer who keeps everyone at arm’s length, the young Shadowhunter soon finds his walls collapsing after he meets Clary, a would-be Hunter who challenges his notions of humanity and rekindles his compassion for others.

At 24, Campbell Bower has already appeared in the Harry Potter and Twilight series, so finally receiving his own franchise seems like a simultaneous opportunity and challenge.

Spinoff Online recently spoke with Campbell Bower in Los Angeles, where the gregarious actor charmed a room of journalists while reflecting on his impending fame. In addition to talking about handling the newfound exposure, he discussed the challenges of finding creative challenges in an industry built on moneymaking vehicles, and offered insights into what about Jace appealed to him – and how he connected his own behavior to the character.

Spinoff Online: Talk about how you define the character, because he possesses an obvious strength, but he also has a sort of mercurial attitude about Clary.

Jamie Campbell Bower: The one thing that stuck out for me upon reading the books, and obviously when there’s an adaptation you have to condense, because you don’t want [the character] to seem schizophrenic. I mean, yeah, Jace is a little bit schizophrenic anyway, but I didn’t want to make him too mental. But there was this vulnerability, and I think it comes from the loss that he suffered from his father, from his parents, so this vulnerability comes through, and his comeback to that vulnerability is this wall of sarcasm and this wall of rudeness. So how did I get there? Well, we all do that sometimes to a certain extent, so I would check myself when I was doing that, and go, so why am I doing that? What’s my reasoning for doing that, and how am I doing that – if Jamie does it this way, how would Jace do it? And then I also made a mood board of fan art, pictures of myself, pictures of Lily, and then people that have had this sort of strength but also this vulnerability, like River Phoenix, Heath Ledger, young Johnny Depp. And then I had the aggression side of Jace, so I used images of a very young James Hetfield. And so when I would be getting cloudy, that would be where I’d go to. The greenhouse scene where he opens up to her is the most poignant moment for him; the character development for Jace is pretty linear, whereas Clary [goes up and down] in every goddamn scene. I would do that for love nor money – you couldn’t pay me enough to do a job like that. So that point where he opens up to her is incredibly important, and that’s why I made him so snarky and dark at the beginning that when he does that, you go, “I get it.” It’s the father thing, but then him not really being able to connect with anybody because of the fact that all he’s done all his life is just hollowed himself out.

How does it feel to be part of now potentially two huge fantasy-oriented film franchises?

It’s amazing. I mean, by no means has it been a career move. I just wanted to be involved in great stories. The reason Twilight happened was because I wanted to play Edward, and I didn’t obviously, so when the second movie came around and they were like, “Do you want to be a part of it?” I was like, absolutely! And then Potter, they just called me up and went, “Do you want to be a part of Harry Potter?” And I went, ab-so-fucking-lutely, yes, of course I do (laughs).

With Harry Potter it seemed like every British actor appeared in at least one film.

Yeah, who’s out of work right now? Let’s go through the list. That’s also why I [wanted to be in it]: I was like, look, the most amazing people pop up in Harry Potter. Like Dawn French pops up, like in a painting, and I was like, I’d kind of like to be a part of that! And in Potter I was a little bit older, but it was a massive part of growing up, and a massive part of my brothers growing up, particularly.

Isn’t there a significant difference in playing a supporting role and then taking over the lead in another one of these films?

Absolutely. Obviously, being the male lead in a studio film, whether or not it’s a franchise, is a terrifying prospect. It comes with responsibility, it comes with some negativity, it comes with opening your life up to people. That’s part of it, but that’s what I’ve been striving to do because that’s what I want to do. I want to push myself; eight years ago, all I wanted to be was in the chorus line of a musical on stage in the West End – and I still feel like that, but the fact that I’m doing this now is bizarre to me. But what’s been great about being a very peripheral part of the huge successes that were Twilight and Harry Potter was to be able to take a step back from the craziness and look at my friends’ careers blow up, and the craziness that surrounds that. So now, sort of semi-stepping into that, I’m aware of it. And then I suppose the idea of having a solid job for six years is pretty cool. But also, when I signed on for this, we weren’t sure if we were going to go on for even two movies. And yeah, we’re greenlit for No. 2, but until I’m like there on set, it’s not happening. Because movies get said they’re going to get made the whole time, and then they just disappear. So until I’m standing there and I’m saying the lines, it ain’t real.

What kind of adversity have you experienced as the fan reactions to your casting have gone from protest to embracing you in the role?

I have to please them, but I also have to please myself. I’m very much aware of the fact that without those people who bought the books, I would not be sitting here. So one has to give them the respect and the credit that they deserve, but ultimately, I’m sitting there reading the same book – so we’re all going to sort of have a common thought about the character. I experienced a negative reaction when I was cast, but it was more about physicality than anything.

They wanted somebody else?

Yeah, they wanted Alex Pettyfer, because Alex Pettyfer was ripped, and I wasn’t, but whatever. But it’s like, I can go to the gym – that’s not difficult. But I would rather have someone slight me for my acting ability than for the way I look. Because there’s pretty much bugger all I can do about the way my face is (laughs).

Do you worry about how the exposure might change you, if the film becomes a huge hit?

No. I’ve always said that. I mean, I’ve been fortunate enough to be working in this industry for seven years now, and throughout that, I’ve seen kids come and go. I’ve seen people become successful and I’ve seen some people fall flat on their ass. So my line has always been, I’m Jamie, and I grew up in the English countryside. That’s who I am. I have a tattoo on my leg of a bird called a house martin that goes back to roost at my parents’ every year, and that means to me that’s my roots – and I’m never going to forget that. Am I going to change the way I do things in my life? Not really. Am I going to walk down the red carpet with a cigarette hanging out of my mouth? No. But I’m definitely going to be who I am.

The Mortal Instruments: City of Bones opens today.

Related: The Mortal Instruments Star Lily Collins on What Makes Her Character Different