Tenet is one of the most ambitious action movies in years, but a specific set piece in Mumbai caused problems for leading man John David Washington.
Washington’s character — known only as The Protagonist — has to jump over a balcony, but the 36-year-old actor is scared of heights.
“It forced me to find some courage and, for the love of the art, you jump. I loved every other take of that,” he said at the press conference for the movie.
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Washington confessed that he didn’t make director Christopher Nolan aware of his fear that night and just got on with shooting the scene.
“I'm sure most actors have been there. 'Can you ride a horse?' 'Sure, I can ride a horse.' You say yes and get over it later.
“He was very patient with me on that particular night, so a thousand thank-yous Mr Nolan.
“I usually take notes well. That night... I wasn't, at that particular moment. But I feel like we got it.”
Nolan said Washington “covered it up very well” if he was afraid during the shooting of that scene.
“That night, I just thought you weren't taking the note. I didn't realise you were afraid of what you were doing,” he said.
Nolan added: “It's always incredible to watch actors just rise to challenges. You roll that camera and these guys just want to do the best for the film.
“It's a remarkable thing to be involved with people working at this level.”
The action set pieces in Tenet are among the most ambitious ever committed to celluloid, with Nolan revealing he had early discussions with the stunt team about how traditional hand-to-hand combat moves could be “manipulated through time and over time”.
Robert Pattinson was certainly impressed by working with Washington, describing his co-star as “like Bruce Lee” when it came to the fight scenes.
He added: “It's actually quite stunning. There's not a lot of people in JD's category at the moment.”
Nolan said that the hand-to-hand fights were crucial to get right and so the cast and crew underwent a “very intensive rehearsal period” in order to work out the best way to execute the scenes.
Washington said: “Being an American football player, it's very familiar to me to rehearse and to practice and to rep at it to where it becomes a familiar body language.
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“They say, amateurs practice until you get it right, professionals practice until you can't get it wrong.
“Those months we had with the team training and getting those movements, they were sort of discovering it as I was, so that was pretty cool to know and have this bond over this new frontier of possibilities for fights.”
Alongside Washington and Pattinson, Tenet also stars Elizabeth Debicki, Kenneth Branagh and Aaron Taylor-Johnson, as well as Nolan stalwart Sir Michael Caine.
The film is a complex sci-fi adventure that marries the scale of a James Bond movie with the tricksy concept of “time inversion”.
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Tenet is due to arrive in UK cinemas from 26 August, with the Stateside release coming on 3 September in the multiplexes that are able to open their doors.