Over the years, Stephan James has established himself as one of Canada's finest dramatic actors with a reputation for playing historical figures in acclaimed films.

In 2013, he was cast as civil rights activist John Lewis in Selma, Ava DuVernay's Martin Luther King Jr. biopic. It was a major breakthrough role for the young Canadian actor — and he says the opportunity was only made possible because of a movie trailer he appeared in for less than three seconds.

In a live on-stage conversation with Q's Tom Power at the Banff World Media Festival, James recalls how British actor David Oyelowo (his co-star in Selma) recommended him to DuVernay after seeing him in the trailer for the sports drama When the Game Stands Tall.

"I'm in the trailer of this movie for, I kid you not, like two and a half seconds," James says. "David Oyelowo, who's a fantastic human being, a fantastic actor, he had taken his kids to the movies. And one of the previews was When the Game Stands Tall…. I'm not sure what provoked him to be like, 'Whoa. That guy should be John Lewis.'"

After the news reached James that he was being considered to play Lewis, he enlisted his little brother to help him make a self-tape using one of his bed sheets as a shoddy backdrop.

"I had to do 15 takes, of course, because I was like, 'Ava DuVernay and Oprah are going to see this!'" he says. "I sent in the tape, and I kid you not, maybe 20 or 30 minutes later, I get a call from my agent, and he was like, 'Hey man, Oprah and Ava DuVernay wanna Skype with you.' … The rest was history."

If you want to see what was so impressive about James's brief performance in the trailer for When the Game Stands Tall, you can check it out below (he appears at the 0:57 mark).

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Interview with Stephan James produced by Catherine Stockhausen.