There's a lad sitting in a chair on a studio film set. He's clearly doubling up for the real star whilst the production team set the lights and the microphones. We can see that it's going to be one of those potent scenes that will stop the show. A real cliffhanger! Then the real actor takes his seat, the make-up artiste does her work and we pan gently to the man who has just vacated the shot, standing in the wings. He knows the words and the actions by heart, there's just one really important difference... I sort of guessed what was going to happen from quite early on, but feared the…