I had watched this film in high-school, as we were studying Peter Barnes (Red Noses was playing at the local theatre).
The Ruling Class is not an easy film to take, and I don't say that because of the musical numbers. It's about a man who, for all intents and purposes, is God, but a loving and forgiving god. He's an affable fellow, given to flights of fancy.
It's when he's made sane that things go downhill.
One form of insanity takes over the other and it is very dark indeed.
What I do love about watching this is seeing Nursie when she was young.
Having destroyed or eliminated everyone who both knew him when, or stands in his way, our reformed psychopath takes his rightful place amongst those who rule us.
It is a bitter and cynical film. I still recommend it. You'd have to be crazy to want that kind of power.