Mark Steyn writes:
It’s the scene on top of the tower where Lee’s Saruman gets stabbed in the back by Grima Wormtongue, for which the director, Peter Jackson, wanted Lee to let out a scream.
The actor felt obliged to explain to Sir Peter why that would be all wrong. He proposed to let out a small groan, a quiet gasp, as the air is pushed out of his punctured lungs. The director was resistant, so Lee said: “Peter, have you ever heard the sound a man makes when he’s stabbed in the back?”
“Um, no,” replied Jackson.
“Well, I have,” said Lee, “and I know what to do.'” And from somewhere deep in the recesses of his memory an old SOE agent conjured the sound a Nazi makes when you plunge the knife in.