Long before actor Mark Rylance won an Oscar for his supporting performance as Rudolf Abel in Steven Spielberg’s “Bridge of Spies,” he was about as established as one can get on British and American stages, winning. Tony Awards, Olivier Awards, and Drama Desk Awards galore. Though he’s done plenty of film work in recent years, including the motion capture lead in “The BFG” and a co-starring role in Christopher Nolan’s new WWII drama “Dunkirk,” Rylance always preferred the stage to the screen, and didn’t really grab the attention of most American audiences — albeit on the small screen — till he starred in the BBC series “Wolf Hall.”

Rylance was drawn to acting when he was growing up in Milwaukee, catching the bug by watching TV shows including “Star Trek” and “Voyage to the Bottom of the Sea.” He gave the craft a go when he was 14, and played his first “Hamlet” at 16, before moving back to England a year later, studying at the Royal Academy of Dramatic Art (RADA), and going professional.

In “Dunkirk,” he plays the fictional boat owner Mr. Dawson, one of many British citizens who, on one day in 1940, took part in the real-life rescue of hundreds of thousands of British and French soldiers when they were stranded on a beach that was being attacked by the Germans. The soft-spoken Rylance, 57, talked about the art of acting and about the film last week in Santa Monica.

Q. Is it true that some of your first attempts at acting were when you and your friends were recreating TV shows?
A. I think I was always interested in the idea that you could change your world with imagination. When I was 8 or 9, time seemed to go much slower than it does now, and rather than just be bored, you could imagine something. A TV show such as “Star Trek” gave you very clear characters. So if I said, “You play Scotty, you play Spock, I’ll play Kirk,” you knew what type of person that was. Then you could immediately imagine something and say, “What’s that noise?” “It’s the Klingons! The Klingons are attacking!” “What are we gonna do?” Then you scream and say, “Ahhh! I’ve been shot!” And you could do this for hours. But I remember a point where the other kids said, “No, I don’t want to play that anymore. I’m gonna go out and play baseball.” I realized that it was a thing that was particular to me, that I still wanted to live in my imagination, and live in a story that was more exciting or dramatic than the story of my life.

Q. When you started doing it for real, did it come easy to you?
A. I had an extraordinary drama teacher in high school who introduced us to incredible original musicals and plays as well as Greek classics and Shakespeare. It was always a little odd for me that I was doing it for audiences, for people who were watching. That seemed to be a bit of a sellout, to be doing these imaginary games in front of people. But it enabled me to do it, and eventually to make a profession doing it.

Q. You obviously got used to the audiences, and worked your way up to being a regular in London’s West End and on Broadway. Was it a difficult transition to move into film, where you played for a director instead of a whole audience?
A. Yeah, and film is harder. In theater, you have a direct relationship with an audience, so you get a lot of ideas from them. Not just from what they’re laughing at or when they’re quiet, maybe because they’re bored. When you have a group of people focus on something at the same time, you get ideas in your head from the collective imagination in the room.

Q. In taking on the role of Dawson, you did a lot of research on Dunkirk at the Imperial War Museum in London. Is he based on any one person?
A. He’s based on a bunch of people, very accurately based on the accounts of the time, in books.

Q. So, who is Dawson, as you play him?
A. He’s a man of the land. He has a family and sons, and he has a pleasure boat that he used for going out with friends into the bay or along what’s called the Jurassic Coast, the beautiful coast of southern England. The soldiers were trapped on the beach because the water was so shallow, the big boats couldn’t get near enough, and it was too far for the men to swim out to them. So they needed these little boats, but they didn’t have them in the military. Dawson is like one of the hundreds of civilians who were approached on that day when Churchill thought that only 30,000 or so of these men would be rescued.

Q. You’re working again with Steven Spielberg in his upcoming science fiction film “Ready Player One.” Are you sworn to secrecy, or can you say anything about it?
A. I play the inventor, the computer whiz kid who comes up with this incredible thing called the OASIS. The story is set 40 years from now, and by that time, most people are spending the lion’s share of their day on the OASIS, experiencing things in a virtual world because the actual world has become so difficult to live in.

“Dunkirk” opens on July 21.

— Ed Symkus writes about movies for More Content Now.