I ought to add, my words are simply an opinion based on my knowledge of Derren (I’m a big fan but no uber geek having read only Tricks of the Mind), my own logic, beliefs etc. I think I, along with many others, was hypnotised/unconsciously manipulated through the use of words, sounds, lights...
Your definition of hypnotism is, to my mind, a bit off. ‘Involuntary hypnotism’ is a contradiction of a sort, people who go up on stage are voluntarily putting themselves forward for hypnosis whilst at the same time being of the suggestible type. Yes, hypnosis requires a co-operation but also...
I think there’s a good chance it did happen. Throughout the show there were loud bangs and those red flashes of light. Derren has used loud noises before, such as in the greyhound winning ticket one where he banged on the counter. This, along with the chosen words, confuses and distracts. Maybe...