LONDON: Like the subjects of his new film, George Clooney took a chance on a group of actors to transform them into believable professional rowers for “The Boys in the Boat”.

The sports drama tells the true story of the inexperienced 1936 University of Washington rowing team which went on to beat Ivy League teams and compete for gold at the Berlin Summer Olympics.

Directed by Clooney, the film is based on the best-selling non-fiction novel by Daniel James Brown.

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“When we started casting, we called them and said ‘now, are you an athletic person?’ And we said ‘you have to be honest, because if you’re not, we’ll fire you,” Clooney said in an interview at the movie’s premiere in London on Sunday.

“And all the guys we got said they were, and they were. It took about three months of training, but we got them there.”

Set at the height of the Great Depression, the film centres around poor student Joe Rantz, played by Callum Turner, who tries out for a place on the eight-man team after finding out it comes with pay and a bed. Actor Joel Edgerton’s coach Al Ulbrickson has his job cut out to turn his chosen candidates into a professional team that rows in unison and can match their top-level rivals.

The actors trained about eight weeks under former Team GB Olympic rowing coach Terry O’Neill.

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“We were just set up to succeed, basically. We had nutritionists and trainers,” British actor Turner, 33, said. “Terry O’Neill won a gold medal in Atlanta. He was training us. It’s the closest thing I’m ever going to feel to being part of a professional sports team.”

Clooney, a fan of Brown’s book, set out to make an uplifting movie, he said. “We’re kind of in need of some nice stories right about now. It’s a story that makes you feel good.”

‘The Boys in the Boat’ is out in cinemas in the U.S. and Canada on Dec. 25 and globally in January.

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