For a theatregoer, credulity has its pluses and minuses. It helps if you can believe that a ghost is appearing on the ramparts of a Danish castle, or that an elderly earl, oddly named Gloucester in an era before Gloucester existed, can fall on the floor and think he’s jumped off the white cliffs of Dover. But I am more credulous than maybe I should be. I ought to believe that Derren Brown is an illusionist, a conjuror and such. He isn’t. He’s magic and doesn’t dare admit it, maybe fearing some born-again witch-hunter will pounce.

Would you please tell me how Brown can fling frisbees into the stalls, bring up the people who happen to have caught them, ask them them privately to think of something and then either tell them what’s in their minds or, better, remove a card describing their unrevealed thoughts from an envelope? How can he get men to cover playing cards in tin foil and correctly identify whatever emerges? That’s the more magical because he’s just broken the customary code and shown us how something similar was done by a Russian woman who conned the KGB into spending zillions on parapsychology. She saw quick reflections of the cards as they were placed on the foil. Brown stands apart and still gets the cards right.

He ends up asking us not to reveal much about “Enigma” and needn’t always have bothered. His final piece of wizardry is so intricate that it would need Merlin to perform it and Einstein to describe it. Somehow he accurately predicts how seven men will themselves decide to stand in front of alphabetical letters holding images varying from an egg to a needle. As an episode it’s too long and, I felt, rather a waste of his skills. Can’t he use his powers of prediction on something useful, like the end of the recession or the future of his less gifted namesake, Gordon?

He’s a personable chap, too: brisk, bright, jokey enough to warn the first-nighters not to risk going into a trance if they have diabetes, heart trouble “or are particularly litigious”. Myself, I didn’t succumb to his mass hypnotism, maybe because I’m in my own kind of trance already, but several did so. That was the one point when I wondered if he used plants, only to dismiss the thought as unworthy. Brown’s only plants are surely the magic herbs in his windowboxes.

The evening’s highlight was the re-creation of seances, complete with weirdly ringing bells and flying paper. Those 19th-century mediums, he said, were conscious or unconscious cheats. Oh yes? They were spooky and so is he.

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