Ridley Scott revealed Idris Elba had a terrifying moment while shooting “American Gangster”.

The movie maker told the Daily Mail how Elba thought he’d been shot by Denzel Washington after Scott tricked him with the recoil of the empty gun.

In the scene, Elba’s character Tango is shot in the head by Washington’s Frank Lucas. Says Scott: “He’s in the cafe and he says ‘Just stay here’ and he goes out and all his brothers are watching, and he goes down the street, and Idris Elba is standing there saying, ‘Hey, what are you going to do, shoot me, Frank? Go on, shoot me Frank, in front of all these people.'”

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“And he just goes boom and shoots him on the spot.

“What happened was, I said to Idris, ‘Listen, when he puts the gun to your head lean on the gun’ — because by the way this is a gun with a solid barrel, there is no aperture, I would never risk it — but when you pull the trigger there’s a recoil, there’s no blank, nothing.

“So I said, ‘I want you to lean on the gun,'” Scott went on, adding that the movement from the gun made Elba fall to the ground.

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Scott said: “He pulled the trigger and it goes bang. Idris thought he’d been shot and dropped to the sidewalk and said, ‘I’ve been shot!'”

Despite Elba’s scary on-set moment, firearms expert Paul Biddiss, who works with Ridley, insisted the filmmaker is “very hot on safety.”

Biddiss explained: “What he was referring to by a solid barrel is a completely filled in barrel that no bullet would be able to pass through, so it was a completely deactivated impractical gun, as far as firing anything was concerned.

“But he was still able to create a recoil effect for the film’s purposes by using something used in films called a UTM round, which can be put in a weapon that has had the barrel completely filled, and it still causes a blowback.

“It is like a small silver case with compressed air that reacts. It can be used repeatedly for a recoil effect each time.

“It’s quite often used in close-up execution shots in films.”