That's what's so satisfying about acting. You can come as prepared as you like, but there's no accounting for what's going to come at you from the other actor. That's part of the joy and the play of it. If you don't have that it's a different kind of performance.
It is doubtless wise, when a reform is introduced, to try to persuade the British public that it is not a reform at all; but appearances must be kept up to some extent at least.