But that is the challenge Anne Wilde has taken up, as a sort of unofficial spokeswoman for the polygamists of Utah. There is a mystery to why this woman should be devoting herself to the cause when she has no apparent personal connection to polygamy, but we will come to that later. For now, she is sitting in her kitchen in Salt Lake City, explaining why taking multiple wives - "sisterwives" - is a necessary prerequisite for reaching the highest level of Heaven.

Wilde's purpose is made particularly tough because polygamy gets a consistently bad press, fuelled by events in some polygamist communities that appear to be anything but celestial. Today, the "Prophet" of a polygamist community in Utah, Warren Jeffs, will be brought handcuffed into court and the evidence presented in public for the first time. He is charged with assisting the statutory rape of a 14-year-old girl, who had allegedly been forced into a spiritual marriage with her cousin. The girl was said by prosecutors to have been ordered to "multiply and replenish the earth" - in other words, procreate - or risk eternal damnation.

Jeffs was the spiritual leader of the Fundamentalist Church of Jesus Christ of Latter Day Saints, a group that detractors call a cult, which is concentrated in Hilldale, a small town straddling the southern Utah border with Arizona. His lawyers will argue that to commit him to trial would be to continue the persecution Utah's polygamists have suffered since the late 19th century.

To a degree, Wilde would agree with that. As one of the leading historians of the practice, she describes how it has its roots in the early days of Mormonism, the Church of Latter Day Saints, which is the dominant religion in Utah. It was the founder of the Mormon church, Joseph Smith, who first revealed the principle of celestial - or plural - marriage in the 1830s.

It was persecution, says Wilde, that forced the Mormons to drop polygamy in the 1890s when the federal US government gave them an ultimatum: end its practice or forfeit all your lands. The church elders did as they were told and in return were rewarded with the granting of statehood to Utah in 1896.

But there were many refuseniks, who were driven underground, excommunicated by their own church. Though the Mormons deny any connection now to the polygamists, the latter continue to claim a common ancestry, calling themselves Fundamentalist Mormons, much to the annoyance of the official church.

The polygamists have also been regularly targeted by the civil authorities. In 1935, polygamy was made a crime in Utah, punishable to this day with five years in prison. But at this point Wilde's account and that of Jeffs' lawyers would probably part. She believes that in recent years there has been a thawing of relations between the civil authorities and Utah's polygamists. In an unwritten pact, the state's attorney general has made it clear that if they keep the law in all other respects, the felony of polygamy will be overlooked.

So it is no coincidence that Jeffs is being prosecuted for assisting the statutory rape of an underage girl, rather than for the many plural marriages he has presided over. Other recent prosecutions of Hilldale residents have also focused on underage sex and on the widespread abuse of state benefits to support plural wives.

I talked to several teenagers who fled Hilldale and they too said that they wanted to escape not because of polygamy per se but because of the increasingly harsh and bizarre way in which Jeffs allegedly ruled over them. Take Joe, a keen, bright-eyed 18-year-old who left the town two years ago and is now living in Salt Lake City. Using a false name as he hopes to remain in contact with his parents, he recalls a childhood with his mothers and 31 brothers and sisters where the two families lived happily in the same house. "Things were good. But then every one of us felt the change."

The change happened when Jeffs took over as leader, or Prophet, when his father died in 2002. Before the change the rules were stringent, but afterwards they became strangulating: no more hiking in the countryside, bicycles, swimsuits or computers. Jeffs forbade T-shirts and bright colours, particularly red, the colour of the devil (an irony as he was caught wearing a T-shirt and driving a bright red car). Long underwear and long shirtsleeves and trousers had to be worn at all times, buttons done up. Pop music was out, to be replaced by tapes of Jeffs preaching.

Fawn Broadbend ran away almost three years ago, when she was 16, and now also lives in Salt Lake City. She remembers before she left being told not to laugh, but that was not why she fled Hilldale. At the age of 14 her name was added by her father to the "joy book", a list allegedly collated by Jeffs of young girls whose parents believed they were ready to be put out to marriage, often with a husband who already had one or several other wives. When Broadbend learned that she was in the book, she resisted: her elder sister had become the 23rd wife of a polygamist with 106 children in Bountiful, an outpost of the faith in British Columbia, Canada, and she didn't want that for herself.

In January 2004, fearing that she could be married off with just 15 minutes' notice, as had happened to others in the community, Broadbend ran. The day before had also proved to be the final straw for her when Jeffs had called an extraordinary meeting of townspeople. In front of a crowd of 1,500, he read out a list of 21 of the community's fathers, telling them they had sinned but without telling them why, and ordering them to leave immediately. All 21 men packed their bags and were gone that night. Most of them are still expelled from the town, separated from their wives and children, frantically trying to work out which sins they must repent.

Many teenaged boys were also turfed out of the community. Chuck, also a false name, is 15. Last December he was called in to a meeting of church leaders in Hilldale and told he had broken the rules by wearing T-shirts and going to the cinema. He was told to leave by the following morning. Diversity, a group in Salt Lake City that works with teenagers thrown out of Hilldale - the Lost Boys, as they are known locally - puts their number at up to 1,000.

At its most extreme, the reign of Jeffs saw families torn apart at his whim. Carl Holm, 42, was ostracised by the church elders several years ago for having married outside the religion, and now lives in Salt Lake City. His sister is one of more than 40 women in Hilldale believed to be married to Warren Jeffs (he is said to have more than 60 children). Two other sisters were married to the same man - a common practice in Hilldale - until Jeffs stepped in and ordained that one of the sisters was no longer to be married. Again, without being told her sin, she was banished from the family. All her children were "reassigned" to the other sister.

Broken families, kids cast asunder, father wrenched from son, sisterwife from sisterwife: there is little sympathy for Jeffs from those who were forced out. "I'd like to see him behind bars," says Joe, now dressed freely in T-shirt and jeans. Why? "The way I see it, God is a good person. He would not do those things to families."

So what of the polygamists themselves? What do they think of the prosecution of Jeffs and of the future of their way of life? Utah polygamists are notoriously secretive. The community of Hilldale has been closed to the outside world for months as Jeffs issued an edict before he went on the run that excluded contact with outsiders. I made approaches to several other groups and churches but no one wanted to talk.

And that is how I ended up in the kitchen of Anne Wilde. She is an expert on Utah polygamy who has co-authored one of the most informative books on the subject, Voices in Harmony: Contemporary Women Celebrate Plural Marriage. Going to see her would, in the absence of actual polygamists who would talk, at least give me the context.

I asked her why, as someone with no personal connection to the practice, she had written such a book. Oh, but she had, she said. For 33 years she had "lived the principle" within the independent tradition - a loose affiliation of men and women who see themselves as being more moderate and reasonable than the Hilldale community - the acceptable face of polygamy. She was the second wife of Ogden Kraut, who also wrote about the religion. There is no mention of that in her book, she explained, because she feared prosecution, but since her husband's death four years ago she has gradually come out, revealing her unconventional marital arrangements for the first time to many of her family, some of whom had ostracised her.

She wouldn't say how many sisterwives she had had, other than "a few", all but one of whom were now dead. She had been unable to have children with Kraut so instead they had written books together on polygamy.

She says that Kraut treated all his wives fairly, not equally, as one wife might be more needy than another. The fact that he was with her only periodically meant that she had more freedom, she says, "as there were others around to cook his food and wash his clothes". She keeps stressing that she feels that being a polygamist gave her more, not less, independence as a woman; and although her husband was a patriarch, part of his role as head of the family was to treat his wives with respect.

Jeffs does not fit into that definition. His mistake, she believes, was to try to find utopia on Earth where perfection is unattainable. But she says that the unhappy experiences of the few in Hilldale should not be used to discredit the many. We are back where we began, to Wilde's public relations campaign for a most unfashionable creed. "I want you to know, I was totally happy in it. Ogden and I got on absolutely beautifully. We had 33 years of glorious, loving marriage."

Polygamy as liberation - is it really time to rewrite the annals of feminism? Not at all, says Broadbend. Her upbringing and education, what little she had of it, was all about female subservience. Even before Jeffs came on the scene she was being taught her role in life: "Girls are put on Earth to obey the man who is superior. We are here to bear children for him and to do his bidding. You do what your man says, and you certainly do not question him. If I had stayed I would have had no say at all over my own life."

Anne Wilde's job as public relations consultant has some way to go.