I have never read a self-help book and consider myself immune to out-of-body experiences. Meditation bores me and the few times I tried yoga, I ended up inexplicably angry.

Above all, what I most certainly do not do is stand up in front of 200 people who openly talk about sharing, loving and personal journeys, and apologise for getting it all wrong. Except, as of last Tuesday, I apparently do.

This is how it happened. When I signed up to a course held by Landmark Education, I wanted to investigate tales I had heard about a course that turned intelligent, predominantly middle-class professionals into strange automatons.

Students were said to lose all sense of themselves and take to phoning loved ones late at night to bring up long-forgotten arguments while excoriating themselves for real and imagined character flaws.

A quick look on the internet revealed even more dramatic claims. Since its creation in 1991, Landmark Education has been described variously as a cult, an exercise in brainwashing and a marketing trick cooked up by a conman to sap the vulnerable of their savings.

Landmark rebuts such claims. Not satisfied with simply transforming the lives of its students, it promises to deliver the secret of what it means to be human and guarantees them futures greater than they could imagine.

For £275 and 39 hours of my time, it seemed like an offer worth considering. In my head, however, I had already begun to draft an article about a society so needy that even its educated elite were mugs enough to pay through the nose for such vague, preposterous promises.

Mugs or not, over the past two years, Landmark has experienced an astonishing surge of interest. While most companies congratulate themselves on achieving a 6 per cent growth, Landmark boasts a steady 10 per cent rise in customers across 100 cities and 21 countries.

More than 125,000 people in the world participated in Landmark's courses last year. In 2001, its revenues reached $56 million, although the organisation is struggling to recover from the destruction of its main New York office in the Twin Towers.

But it is on Britain's cynical shores that the organisation has struck gold, attracting more than 1,050 students each month, 80 per cent of whom go on to take a second course.

Questioning former students on what the course taught them got me nowhere: happy to talk, they spoke winningly of transformations and breakthroughs, insights and possibilities while remaining vague as to how such magic was achieved. Clearly, the only way to get to the bottom of the course was to attend myself. So it was that three weeks ago, I reinvented myself as a human resources manager for an unspecified City firm, and signed myself up.

It was with mild trepidation that I took my seat on Friday morning in the all-white lecture hall in Landmark Education's rented north London offices. I had three days of lectures ahead of me, each day lasting 15 hours and seemingly designed to induce mild sleep deprivation. Still, I had been guaranteed a transformation by Monday morning.

We sit in rows. On the stage in front of us, 53-year-old Jerry Baden perches on a director's chair and twinkles at us with dark eyes. Below him sit 160 students, aged from 18 to 84, with the majority in their thirties. There is a fairly equal balance between the sexes and we are a reasonably representative ethnic mix.

On the floor beneath us, are 100 Forum graduates taking the £495 Advanced course. Two floors below, another 100 students study the £90 Self-Expression and Leadership programme. The building practically throbs with budding transformations.

People look apprehensive. There is much twisting of hair, shifting in seats and quick, covert glances around the room: everyone seems to be wondering what they have got themselves into.

Jerry is bombarding us with grand claims: Landmark Education is so powerful, he says, that it could achieve world peace if used correctly. He slips in a reference to Arafat and Rabin shaking hands in the rose garden; it was a Landmark moment, he claims. Really? Our eyebrows have barely time to arch in cynical disbelief but he has swept on.

World peace aside, this course will transform our lives, he promises. Transformation will come to all, but individual moments will vary: like corn, we are told, we will pop at different times.

'But not all popcorn pops,' I think, momentarily panicked by the sure knowledge that I'm going to be that one last kernel, left charred and blackened at the bottom of the pan.

Jerry sweeps on. To pop, we must make ourselves coachable. We must not, he emphasises, choosing the one word guaranteed to strike fear into my soul, be observers. He seems to look straight at me. I kick my notebook under my chair and sit up straighter.

There are rules. Timekeeping is essential, toilet breaks are discouraged: missing even a minute will jeopardise our chance of achieving transformation. We will work for three to four hours at a time. During short breaks, we will have homework. There is one meal break in the early evening and more homework after the day is done. Notetaking, unprescribed medicines and alcohol are forbidden and we must open our minds to all suggestions.

Are we being lulled into dangerous credulity? We discuss it anxiously in corners during our first break. Are these mind games? Is this how brainwashing begins? We glance over our shoulders as we whisper together to see if we are being watched. Comforted, I think, by the discovery that we all share the same anxieties, we begin to relax. We start to take active responsibility for each other and a community is formed.

Over the next three days, we are educated in a mix of philosophies, psychology and religious theories, illustrated by readings from books, plays and one detailed description of the entire plot of Citizen Kane. Including the ending.

The theories expounded cherry pick ideas from existential philosophy and motivational psychology. They take in aspects of Maxwell Maltz's psycho-cybernetics, Zen Buddhism, Alan Watts and Freud. Shadows of Abraham Maslow, Hinduism, Dale Carnegie, Norman Vincent Peale and P.T. Barnum flit over the proceedings.

We're encouraged to share and, schooled by Oprah in what to do with a platform and a neurosis, people rush to the microphone to have Jerry lay waste to their tales of parental neglect, social deprivation and emotional hardship. It's useful but not rocket science and I remained stolidly unpopped. We've been sitting in the same, hard chairs for almost 13 hours. I'm bored and my back hurts.

There are two more hours to go before we can go home, by which time my last train will be long gone. I begin to get cross. I suspect I'm losing what little coachability I might once have possessed.

Next morning, we retake our seats. Everyone in my row spent hours on their homework. I unwound instead by reading P.G. Wodehouse and criticising the course with my boyfriend. I feel bad.

I've had kinder starts to the day. We're still taking our seats when Jerry begins shouting: We're ugly people. Disgusting. Our behaviour is entirely governed by a need to look good which makes us liars, fakes and frauds.

'You're disgusting,' he shouts. 'You just don't realise quite how disgusting you are yet.' He pauses. 'But you're just about to find out.' His timing is impeccable; we've hardly woken up and we're already hanging on his every word.

This morning, he says, he is going to force our resistant minds to recognise how fetid and mean our personalities are. He shouts, he mocks, he refuses to let us ask questions. He tells us we're liars and ridicules the stories we tell about our own lives.

I can hardly bear it. I resent the way he struts across the stage and the way he takes stock of us all, smoothing the pleats in his trousers and patting his hair. I find his confidence intolerable and am maddened by his belief that he knows us better than we know ourselves. And yet, I am gradually forced to admit that he might be right.

One after another, Jerry lambasts those who take the microphone to complain about how hard, harsh and unfair their lives have been. He pushes them through stages of anger, tears and denial until they stand face to face with their own delusions, deceits and contrivances.

Jerry knows he's won. Now that we're putty in his hands, he launches his bombshell. For every relationship that has failed, it is up to us to make it right. And now. In the next break. It's time for that phone call.

He asks for a show of hands: who will make the call. A smattering of hands go up. Too few for Jerry, who tells us to begin the conversation with the words: 'I've been making you wrong for...', 'I've been resenting...' or 'I regret that...'.

There are more hands in the air now and Jerry ploughs on. However we choose to begin the call, he says, we're to end it with the unambiguous, unilateral statement: 'I love you.' A few people take their hands back down.

By midday, the pressure to make the phone call is so intense that people are dialling as they walk down the stairs. Tearful heart-to-hearts take place in public corridors as once-implacable feelings of hurt and recrimination turn to reconciliation in a few short sentences.

I do not make a phone call - I feel I have no one to call - but I see how brave and strong others are to make theirs. I begin to wonder whether it is healthy self-awareness or a deepset denial that make me feel so stable. I begin to prod at the possibility of the latter.

Landmark has faced accusations of being a cult, but I saw nothing of that. Far from working to separate us from our families and friends, we were told there was no relationship too dead to be revived, no love too cold to be warmed.

One girl who complains that she cannot feel close to her own mother realises she has never recovered from seeing her struggle ferociously bring up a young family alone.

'You were scared of your mother at the age of four and have been carrying that frightened child around with you ever since,' Jerry says. That evening, she phones her mother.

'I didn't even realise I was doing it because the feeling had become so familiar,' she says next day. 'It's only now I've stopped being scared of her that I realised how it had affected our relationship.'

By the third day, nearly everyone except me seems to have popped. One man who has called everyone in his phonebook describes his newfound joy to another man who has just rung every woman he has ever slept with.

People are straining at the leash to take their new-found confidence out into the real world. Everywhere, plans are being made; careers are reinvigorated and lives overhauled.

I wish I could be part of it but, apart from recognising a couple of useful lifestyle tools, I remain out in the cold. Eventually, I realise I'm breaking the promise I made to be coachable. I decide to stop analysing, and simply give Jerry my trust. The words sound extraordinary in my mouth: this is not what I do.

As a semi-interloper, I don't feel I have the right to go up to the microphone but at the next break I ask Jerry to show me how to mend a once-strong relationship that hit a barrier.

'We make others wrong so we can be right and you just love to be right, don't you?' he says. His words mean nothing to me. I don't understand. Jerry speaks as though to a child. Chastened, I accept his condescension; I realise his words will change my view on not just this relationship but on others.

I struggle and dimly begin to see his point. If my friend didn't regard what she did as wrong then there are at least two versions of her intention. If there are two interpretations of anyone's meaning, there might be dozens. If, therefore, there is no absolute truth, then whatever I believe about someone else's intentions says more about me than about them.

I feel pins and needles run down my legs. I realise I have, finally, popped. Now I have to make that call.

'Just tell her you love her,' Jerry concludes, getting up. I don't want him to go now. I want him to stay for ever and advise me. 'Isn't that the only thing you know for certain?' he asks. 'Just tell her what you know to be true.' And I do. It's easy, surprisingly so. In a single phone call I get a friendship back. She tells me she loves me too. I cry and am happy.

Two days later, after a tentative excursion into the real world, we return to compare notes. I cannot find a single person who believes their life hasn't improved.

We're invited to come up to the microphone and share. It is Doug Tucker, a 35-year-old hot tub salesman from Stratford-upon-Avon who puts it best. Over 6ft 4in, with a shaven head and rippling biceps tattooed with a snarling bulldog and the England flag, Doug is hardly the middle-class professional the course appears to attract.

'If anyone who knew me before I came on this course said I would even be in the same room as a bunch of people clapping and saying they loved each other, I would have hit them,' he says. 'Likewise, if anyone had told me I would have realised things about myself that I've realised in the last few days, I would have laughed in their face.'

'This course has transformed me. And the funny thing is, I didn't know I even had it in me to transform,' he smiled.The Landmark Forum is not magic. It is not scary or insidious. It is, in fact, simple common sense delivered in an environment of startling intensity.

It is this intensity that makes the difference. While any one of us might well have already been told the same home truths by friends and family, we were too distracted by life and too wrapped up in our own defence mechanisms to listen.

Landmark takes you away from life. The three days create a bubble of possibility in which we were able to try on new opinions and experiment with fresh behaviours.

I don't know whether I will apply every lesson in the future, although I hope I will. I'm simply going to trust Jerry when he promised it was like riding a bicycle; that once we learn how to balance, we never forget. Although we might, every so often, still fall off.

Secret seven

The Landmark Forum's 'seven commandments' for being an extraordinary person:

· Be Racket-Free: give up being right - even when you know you were.

· Be Powerful: be straight in your communication and take what you get.

· Be Courageous: acknowledge your fear (not necessarily get rid of it) and then act.

· Be Peaceful: give up the interpretation that there's something wrong.

· Be Charismatic: give up trying to get somewhere. Be entirely fulfilled in the present moment.

· Be Enrolling: share your new possibilities in such a way that others are touched, moved and inspired.

· Be Unreasonable: in expectations of yourself and others beyond what you would think they are capable of.