Picture the scene: you are in a room with more than a hundred adults. Sitting at one end, with a microphone in his hand, is a man with long white hair who is encouraging everybody to introduce themselves to each other. "Go up to somebody," he says, "and say one honest, true thing about them that strikes you immediately. Then have them do the same back to you. But before you do that," he goes on, "please take off all your clothes."
Welcome to the "most radical self-help workshop in the world", as this hip new 10-day residential retreat is dubbed. Led by the Birmingham-born life coach guru Paul Lowe, it is not a place for the shy and retiring. As well as being encouraged to voice compliments to each other, such as "you make my vagina tingle", discuss innermost feelings in intense, nude "sharing" circles and take part in sensual massage sessions, participants will also be invited, during the course of the workshop, to explore their sexuality with multiple partners (yes, actually in the workshop). In Lowe's eyes, you see, monogamy is one of those "ludicrous, unnatural social conventions that stand between you and spiritual enlightenment".
And if it sounds like a weird hippie sex cult or an excuse for free love - well, it is. Hugging trees, banging bongo drums, unleashing the warrior within - it's all back in vogue. If you are in the spiritual self-help loop, you will have heard of the Landmark Forum (with a reputation for cult-like motivational workshops), the Hoffman Process (where you bash baseball bats into cushions), even the Secret Science retreat (where you tread hot coals in the Atlas mountains). They are, in a way, the 21st-century version of Est. (Remember Est? The Ehard Seminars Training, a break-you-down-and-build-you-up workshop of the early 1980s, where you had to stand on a plinth in front of hundreds of people and point to all the bits of your body you hated most.)
What really goes on in these workshops is often hidden from view, but a new documentary of a Lowe retreat, held just outside San Francisco, with some of his followers, many of whom are from the UK, reveals that taking one's kit off is just the half of it. First, we meet the filmmaker, Jamie Morgan, 47. Jamie was inspired to make the film after he had yoga lessons with Ryan Spielman at the trendy Triyoga studio in north London and, through him, heard about Lowe. As the narrator of the film, Jamie tells how he has a beautiful French girlfriend, Sophie, whom he is worried about hurting, but at the same time feels compelled, as an explorer and artist, to face up to his commitment issues and see what it is like to live a different way. As Lowe explains: "Most of our neuroses are tied up with our sexuality. Once we are totally comfortable with our sexuality, that is when our neuroses disappear and we start connecting properly with our spiritual flow."
Meanwhile Ryan, 29, whose former clients include Madonna, Sting and Trudie, has no such commitment issues and has attended the workshop many times. Indeed, it was at his first workshop that he met his former wife, Lowe's daughter, by whom he has a three-year-old son, Jasper. A staunch antimonogamist, Ryan is now going out with Maddy, 31, who has come to the workshop to see if she, too, can brave the idea of a fully open relationship.
Then, there is Laurel, 31, who is happily married to an artist back home, but is nonetheless eager to explore her sexual identity and confront the nagging feelings of panic she has about remaining faithful to one person for the rest of her life.
Lowe himself, a charismatic, twinkly-eyed 72-year-old with a paunch, sits at the podium dispensing his own particular brand of tough love. It's interesting, but not particularly comfortable, viewing. Take, for example, Ryan's naked yoga routines as he talks to the camera - while Maddy, er, pleasures him - by the pool. Equally pillow-bitey is the scene where Maddy, who is clearly very much in love with Ryan, has to cope with him and Laurel deciding they are so attracted to each other, they must have sex. Watching her crying out on film, after the event, as if suffering physical pain, makes one wonder whether the Lowe lifestyle might be a touch easier for men than it is for women. That said, neither is it pretty watching Jamie tearfully apologise on his mobile to Sophie for the orgy he went to the previous evening and then, eyes still smeared with tears, explaining to Lowe that he is frightened that now he's come this far, he may never be able to go back.
A year on, I meet up with them to find out what the repercussions have been. Jamie is still living with Sophie and claims to be as much in love as ever. "I'm no preacher of antimonogamy," he says, making green tea for me and the rest of the gang in the kitchen of his ultra-modern duplex in Primrose Hill, "but it has radically changed the way I live. Sophie and I now talk openly about our attractions, and we are occasionally sexually active with other people. I still get insanely jealous at the idea of her with other men, but, since the workshop, I 've started to realise I want her to enjoy her life more than I want her, and I want her to have the same feelings for me. But hey, I'm nowhere near as brave as Ryan."
"I guess you could say my primary commitment is not to my relationship, but to my spiritual growth," says the dazzlingly handsome, carefully spoken and conspicuously unscathed Ryan, "and if that sounds selfish, it shouldn't. I mean, what's worse, being madly attracted to someone other than your partner, not having an outlet for that and getting more and more frustrated with both that partner and your children, or living your truth and loving more than one person with that other person's complicity? People in traditional families, they mess up their kids too, don't they?"
Ryan now holds regular weekly sharing groups in London, where Lowe devotees can reveal their truths and, on occasion, if the mood feels right, get naked. He certainly lives by the sword: he no longer goes out with Maddy, and is expecting a second baby by his former wife (conceived with a cup and a syringe because the pair of them, as he cheerfully puts it, "found it weird when they tried to do it the conventional way"). His truth, he says, will always be his son Jasper, but it is also, at the moment, his new live-in girlfriend, Veronica, who was once a "Barbie girl, with the perfect marriage and the perfect nails", as she describes her former self. Then, a few years ago, she went to the workshop in her native Germany and became, like Ryan, a committed antimonogamist.
"It's simple," she shrugs. "I act on my feelings. If there's a tingle, it's a yes. If there isn't a tingle, it's a no. And that's not just about sex, it's about everything, even how you like your eggs. I don't know what my work colleagues think about the way I choose to live my life - I don't really discuss it with them - but it's possible they think it is a little bit strange."
"Look," says Laurel, who is back with her husband after returning from the point of divorce after the workshop, "it's a Pandora's box having that experience. You cannot go back to that secure life, with all your boundaries in place. If you did, it would be like putting a plaster on a huge suppurating boil. But," she goes on, "when I see all these people I know lying, having affairs, suffering from sexual anorexia, feeling miserable, because they are not willing to confront the truth about their sexuality, I know I don't want to be like that."
"It's true, everything is based on monogamy," says Sophie, Jamie's girlfriend.
"I have to admit it would hurt me very much if Jamie were to sleep with other girls, but there are other people I feel sexual towards besides him. As Paul says, 'You can love more than one child, you can love more than one ice-cream flavour, why would you be allowed to have only one lover?' "
She has a point. As Sting once said, if you love someone, set them free. On the other hand, you cannot help think of the plight of so many miserable women out there who agree to open relationships in order to hold on to their men.
In many ways, I'm with Lowe: our neuroses are undoubtedly tied up with our sexuality. There are huge games we play around it, terrible things that happen to us when we suppress our natural desires - and yes, wouldn't life be purer and simpler if we acted on our impulses and got on with it? Yet, when Ryan says that his primary commitment is to his spiritual growth, one can't help wondering whether "spiritual growth" might not be another way of saying "self-interest".
Is it not significant, too, that Lowe is male? According to Ryan and Jamie, he makes no secret of his penchant for pretty young women. Again and again, I think of Maddy, weeping into the camera after being "betrayed" by her boyfriend and best friend. Of Sophie confessing to me that she went through hell when Jamie was off at the workshop making his documentary.
Of Jamie admitting that, in an ideal world, he'd be able to play around and she wouldn't. Radical self-help? This stuff is as old as the hills.
The DVD of The Workshop will be released in the UK on July 21. Details of Spielman's "sharing groups" can be found at trueryan.com.