Tonight Britain’s best-known hypnotist, Paul McKenna, the former Radio One disc jockey, will be found at the Dominion Theatre putting ordinary people under extraordinary spells. Like turning an accountant into an uninhibited Elvis Presley and getting a systems manager to wander around in the interval, deep in trance and behaving (hilariously) as if the 2,000-strong audience is full of long-lost relatives.

McKenna’s show is now a cult fixture of the London theatre scene. Few big-name comedians or pop stars could pack a huge auditorium like the Dominion as many times a year as McKenna does. Many of his fans – and they include people like Ruby Wax, Lenny Henry, Dawn French, Jools Holland, Hanif Kureishi and Barry Humphries – return time after time. Annabel Croft, for instance, has seen his show six times.

Hypnotism has made him rich, clever and the proud partner of a beautiful girlfriend, Clare Fordham, whom he first met nine months ago when she came on stage to be hypnotised. They were later introduced at dinner and now live together. He refers to her as ‘the greatest love of my life’, but quickly denies that hypnotism helped him win her. ‘When people ask whether I use hypnotism to get girls, my reply has always been that I don’t need to. That would be like being a bank robber.’

Today, aged 28, he drives a Mercedes, lives in a £150,000 four-bedroom house in Middlesex – ‘It’s all I could afford five years ago. I’m moving somewhere more opulent soon’ – and is well on his way to becoming a millionaire, although he won’t disclose how much he makes from the shows. Nor how much he might get from the range of self-hypnosis videos – money-spinning tapes on how to improve your sex life, combat stress, slim and quit smoking – which can be bought in most high streets. ‘I watched and studied rich people because I wanted to get rich,’ he says. ‘I found they had things in common, like seeing crises as opportunities . . . But feeling rich is not about having a Rolls-Royce and a big house. It is a feeling of success, confidence and security.’ So he programmed himself with that anyway. ‘And then my earnings increased tenfold. That’s when the show started to take off.’

Not bad for a lad who, in formal academic terms, gained only five 0-levels and one A-level, which was in art. But then he says he has also used hypnosis to improve his IQ and increase his reading speed. ‘A psychologist friend of mine measured my IQ and said it had jumped 20 points. I am going to do Mensa. I would guess it’s around 145 or 150. I’d like it to be higher, off the scale. If you can make a little jump, you should be able to make a big one.’

For the uninitiated, here’s an introduction to his stage act. At the beginning of Paul McKenna’s Show, about 100 volunteers go up on stage and he chooses his participants from those he has successfully induced to lock their hands as if with Superglue. Gradually the numbers are whittled down to about 10 whom he helps to become unwitting comics, without ever humiliating them. He won’t hypnotise pregnant women, or those who are drunk or very stressed. ‘No harm can come to them. But they might start catharting. I don’t want someone on stage alleviating their stress by crying or something.’

Last Friday the audience was very working-class; other times it is full of Fulham stockbrokers. There were three women and 10 men on stage at one point. Is there a difference between the sexes? ‘I find on stage men tend to be funnier than women.’

In front of the audience, McKenna is slick, like a younger Paul Daniels. Off stage, he is a slight, besuited and slightly nervous man who looks older than he is and has hypnotic blue eyes. He talks in a seamless, information-packed, broadcasterly manner, often using pop psychology buzz words, with the patter of a You Can Make Your Life Work salesman. Amusingly, it also becomes apparent that McKenna mirrors, shortly afterwards, every body movement the interviewer makes. ‘Oh dear, no one’s ever noticed before,’ he says. ‘The aim is to create greater harmony for communication.’ McKenna was first introduced to hypnotism at the age of 22 when he worked on Radio Chiltern and invited a hypnotist on his programme. He was hypnotised and amazed at the experience, so borrowed a couple of books on the subject and taught himself. He has never had any formal training. He first hypnotised someone, a friend, in his back garden when he was 23. McKenna then plied his trade doing stag nights, Oxbridge balls and Army bases. ‘My worst experience was with an audience of estate agents when nobody volunteered.’

He had a happy childhood, with the exception of his Jesuit education at St Ignatius College. He is vehement in his hatred of Catholicism. ‘What a bunch of mind manipulators,’ he says, without irony. ‘I couldn’t believe the brutality, mostly mental brutality. You’re guilty if you have sex before marriage. If you do anything, you’re guilty.’ Raised in Enfield, his father is a retired building contractor, his mother a teacher, and his younger brother a surveyor.

At the age of 19 he was developing an interest in eclectic New Age matters, learning from Zen Buddhism, pop psychology, the American psychotherapist Milton Erickson, transcendental meditation and radionics. He had also done exegesis, a weekend of wholesale enlightenment. ‘I think a lot of people who end up in cults are looking for surrogate families. That wasn’t true of me. I did it because a friend said, ‘I’ve just done this course where they lock you up in a hotel room, shout at you for three days and charge you £250. I laughed my balls off’.’

Two years ago, he used the hypnosis techniques he’d been studying to discover what was in his subconscious. ‘I studied the thought patterns of successful people and fed those to my subconscious, and immediately I began to feel so much more in control of my life. I no longer feel victimised. I never get depressed now.’

McKenna takes hypnotism very seriously and uses the entertainment side simply as a hook, ‘to show people that hypnotism works’. ‘If you could bottle hypnotism, it would be the most powerful drug in the world today. But it’s not a panacea.’

To the sceptical, of course, McKenna has simply found an easy way of making money. Debunkers question whether his stage show is fixed (‘I wish it were. That would be much easier’). They maintain that hypnotism is dangerous. And they say that there are good and bad hypnotists and no way of telling whether someone is one or the other.

But he believes it is important for people to discover what they are capable of. ‘Most of us,’ he says, ‘spend more time learning to work a food mixer than we do our brains.’

With fellow hypnotist Michael Breen, he holds seminars to teach people self-hypnosis and has offered courses in self-development, the cure of phobias (‘I charge by the change’) and future-life progression. ‘You can see yourself in future lifetimes, you may be a different sex. It’s like a snapshot of karma, so why not deal with those things now in this life rather than have to go through them in a future life?’ He has also investigated past-life regression (‘Fascinating. People talk in foreign languages’) and is now moving into the corporate world and starting to work with companies on stress control and hypnotic negotiation.

His greatest interest is realising human potential and success conditioning, ‘instead of going to a hypnotist because there is something wrong with you’. To this end, he has been working weekly for the past three months with Olympic fencer Johnny Davis who is ranked 26th in the world. ‘I don’t know if he’s going to win a gold medal, but he tells me he’s vastly improved.’

Psychics and astronomers say McKenna is special. Ask him if he is normal, and he laughs a lot. ‘What do you think?’ But does he feel different? ‘When I was a child, I felt very different from everybody else. And by my teens, I felt incredibly different. I felt everybody else had got it wrong. I didn’t feel exactly lonely or alone. But I don’t find that many people who think like me.’