Over the past year, all the pieces finally began to fit together for Kingsley Ben-Adir.

Foremost among them was the British actor’s breakthrough performance as Malcolm X in Regina King’s “One Night in Miami,” in which he movingly mines the human, vulnerable side of an icon. But there were also roles as varied as Barack Obama in “The Comey Rule” and Zoë Kravitz’s love interest in “High Fidelity.” And then, the most unambiguous sign of “making it”: Ben-Adir even popped up as a character played by guest host Regé-Jean Page on the latest “Saturday Night Live.”

But this sudden rush of attention, success and awards buzz is a heady development for Ben-Adir, who had begun to question everything about his approach to acting only three years ago. “I felt like I was just making it up as I was going along, sometimes hitting and sometimes missing,” the 35-year-old actor said on video chat from his home in London. “And I really got to a point where I won’t say what show it was, but I saw something I had done on television and I felt so depressed by the work. I was like, ‘Is that it? All of the work that went into it, and that’s what it was?’”

Raised on a steady diet of “Inside the Actors Studio” episodes — “I’ve seen every one of those two or three times,” he said — the London-born Ben-Adir expected his passion for acting to be stoked at the Guildhall School of Music and Drama, which he graduated from in 2011. Instead, Ben-Adir got a stiff, technical education meant mainly to prepare him for big British stages. “The training that I had and the training that I dreamed about, they were two completely different things,” he said.

That left Ben-Adir feeling disconnected as he began to put together his career. But acting classes he began taking three years ago with the teacher Victor Villar-Hauser taught him how to better marry head and heart, and without that renewed commitment, Ben-Adir said he couldn’t have made it through “One Night in Miami.” Directed by Regina King, the film imagines a quartet of Black icons — Malcolm X, Sam Cooke (Leslie Odom Jr.), Muhammad Ali (Eli Goree) and Jim Brown (Aldis Hodge) — as they spend one tumultuous night together hashing out their issues.

Ben-Adir was the last to be cast in the film after the original actor playing Malcolm dropped out, and had only 14 days to get ready before the shoot began. “It was a complete whirlwind,” he said.

These are edited excerpts from our conversation.

Why did you have so little time to prep for “One Night in Miami”?

After I auditioned, I kept being promised that I was going to find out in a few days, and those few days turned into a couple of weeks. I was really losing faith that the part was going to come to me, and then we got to the 21st of December, and I said to my team, “Guys, we’re shooting on the 3rd of January. This is insane. What’s going on?” I told them, “I’m out, because I’ve been robbed of my preparation time.” That message didn’t get passed on, so when the offer came, it was a real surprise.

How different would this role have been if you’d had a year to prepare for it?

I would have had an encyclopedic knowledge of Malcolm that I didn’t have going in — I was learning as I was going along. But I don’t necessarily think that’s always helpful, to know too much. There’s something about not knowing and feeling unsure that’s very, very useful to being vulnerable in the moment and just having to trust in everything that’s going on around you. You should be flying into those scenes with your chin out, in full surrender.

In this case, it probably helped that you knew the other characters well: You’ve auditioned to play Sam Cooke in different projects, and you spent years attached to star in a Muhammad Ali movie for Ang Lee that fell apart.

I had a huge understanding of Sam’s history, and I know Muhammad Ali’s story probably better than I do Malcolm’s — that’s how many years I spent working on Muhammad Ali. But without getting too witchy-woo about it, genuinely I feel like it was the accumulation of all the projects and experiences that I’d had up to that point really allowed me to connect with Regina in a way that was equal and collaborative. And what you have in Regina is someone who understood that it needed to be a different Malcolm, a vulnerable Malcolm. A Malcolm we haven’t seen before, a Malcolm in private with his friends.

As an actor, you have to call upon that vulnerability a lot, but at the same time, doesn’t this profession require a thick skin?

Yeah, absolutely. Last week, I realized that my accountant here has been [screwing] me over for six years, and it was a really big wake-up call, because I realized the business and the creative are linked and you have to be on top of both of them. It’s no good to just be like, I’m an artist. No, you need to get a real handle on the business so that you can be really free within your art. In drama school, no one expressed the importance of being sensible with money and how much impact that has on you creatively.

How much impact does it have when you get your hopes up for a big project and it falls through? That Ang Lee film was supposed to be your breakthrough, and then it didn’t happen.

I feel like 95 percent of this job is dealing with disappointments and getting your energy up only to be let down. Something fell through last week that I’ve been working on and off for a year, but I made that work about me and my journey as an actor, and I learned something about myself through that process. Yes, it hurt, and you have to cope, but I feel like working with Ang for those two years was a major lesson in how you do not get your hopes up about anything until you’ve wrapped, it’s edited and it’s out.

You go, “That door’s closed, another one will open. Show gets canceled, that means you’re available for other stuff.” Lots of people I’ve come up with through the years aren’t able to do that, and you’ll become resentful, bitter, and depressed. I feel real disappointment sometimes, but the bigger the disappointments, the better the highs will be when you get them.

If this success had happened when you graduated from drama school, how different would it feel?

I don’t think I would have been ready for this when I was 24, I really don’t.

But I’m sure that at 24, you felt ready for this, right?

More than ready! I was convinced that I should have been walking out of that drama-school building on to playing No. 2 with Brad Pitt. That’s not what happened, but I’m so glad it didn’t, because I know a lot of people who got huge opportunities too early, and they’re not around anymore.

The first time I went to L.A., I was scared away and I didn’t go back for four years because I just wasn’t ready. I hadn’t done enough work on the dialect, and I had some really bad experiences with being stopped halfway through auditions because it wasn’t working. I was really lonely — L.A., if you don’t know people, can be really isolating — and I had no money and a terrible manager who ignored me the whole time I was there.

So I was like, “Let me just go home.” And then I stayed onstage for a few years and let it happen more naturally. All those small parts where I got to be on set watching Brenda Blethyn, Mark Rylance, Michael Fassbender … you take bits.

You’ve said before that part of the reason you came to L.A. in the first place is because your options were limited as a Black actor in the U.K. After the year you’ve had, is that changing at all?

Yeah, massively. It’s hard to talk about offers and stuff without it sounding arrogant, but in the last few weeks since the movie’s come out, there’s 16 scripts. It’s really confusing, and it takes you a second. I was like, This is what you dreamed about. This is it.

I’m so grateful, man. Yesterday, I had a teaching session at 9 on Zoom, and then I had a singing lesson, four hours of script reading, and two movies that I had to watch. How lucky am I? I really don’t need much. My agents hate me saying it, but I know how to live off $200 a week. I don’t want a big car, although I’d like a garden one day. But I am turned on and excited by the possibilities of my life, which is to be with the people I love, traveling and seeing the world, and then making cool movies.