CANNES: British actor Robert Pattinson said Friday he was terrified before making his Cannes debut as a sex-mad billionaire, in part because director David Cronenberg told him it would entail a nude on-screen medical exam.

Pattinson told AFP after the premiere of “Cosmopolis” based on the Don DeLillo novel set in a dystopian New York during the fall of capitalism, that he was amazed at his leap from the “Twilight” vampire flicks to the world's top cinema showcase.

“There's nothing else like Cannes. I was kind of hoping I'd get a movie here maybe in 10 years' time,” he said in a joint interview with Cronenberg.

“It's amazing, it was literally one of the happiest phone calls of my life when my agent called up to say we got in. The script is obscure, it's quite an odd film. I had absolutely no idea what was going to happen with it.”

Cronenberg, a master of artful horror movies about the mysteries of the human body such as “The Fly”, “Dead Ringers” and “Existenz”, put Pattinson through his paces in “Cosmopolis” in which the 26-year-old appears in every scene.

Pattinson, as a financial wizard watching his empire crumble from the back seat of his stretch limousine over the course of one day, has sexual encounters with three women including an odd liaison with a sweaty jogger in which she watches him get a prostate check-up.

“I did get a little bit worried about the prostate scene before, but mainly because you said I was going to be completely naked,” the actor said to Cronenberg with a laugh.

“Five minutes before I was like, 'I don't know if I can do that'. I think you said you were going to shoot it between my legs. That was the one time I was a little bit panicky.”The director joked that such tactics were all part of the psychological preparation of his actors.

“We start at the extreme and then we gradually get reasonable,” Cronenberg said.

“Cosmopolis” is one of 22 films vying for the Palme d'Or top prize at Cannes, to be awarded Sunday.