Here‘s a tape of Alfred Hitchcock speaking to Francois Truffaut in the mid ’60s for the book that eventually became “Hitchcock/Truffaut.” The subject, as Hitchcock described, was “a little matter of the physical aspect of the kissing scene in Notorious. The actors, of course, hated doing it. They felt dreadfully uncomfortable in the manner of how they had to cling to each other. And I said, I don’t care how you feel, I only know how it’s going to look like on the screen.
“I conceived the scene in terms of a desire on the participants not to break the romantic mood. To normally break apart, it’s possible that the moment would be lost. But there were things to be done, movements to be made with the telephone and the door, where it was still essential for them not to break the embrace. And I felt that the camera, representing the public, should be permitted as a third part, to join in the embrace. I was giving the public the great privilege of embracing Cary Grant and Ingrid Bergman together. It was a kind of temporary menage a trois.
Here‘s the best part: “The aspect of not wanting to break the mood…the idea was given to me when I was in a train coming from Bologne to Paris and the train was going through a tup rather slowly,” Hitchcock says. “It was a Sunday afternoon and there was a big factory and there was a large red brick wall, and against the wall was standing a young man with his girl. The girl had her arm linked through his, but he was urinating against the wall. But she never let go of his arm. She was looking down at what he was doing, then she looked around the countryside and then back again, and I thought this was true love really functioning, and that was the actual inspiration for the scene in Notorious.”
Here’s a site with links to several tape portions of the Hitchcock/Truffaut sessons.