I found myself wishing that the tube to Kentish Town would behave like a proper Northern line tube should and get stuck for half an hour in the next tunnel. I desperately needed the extra time. I was on my way to interview Marina Warner, one of the world's leading experts on mythography, and yet I still hadn't quite managed to master the full details of a single Greek myth that I could employ as a casual illustration.

I'd decided that the story of Zeus was as good as any other and with the help of a yellowing Everyman Smaller Classical Dictionary I was just about getting to grips with his family tree, with the knowledge that he was a son of Chronos and Rhea and a brother of Poseidon, Hades, Hestia, Demeter, and Hera. But for someone brought up on the trinitarian simplicity of God the Father, God the Son, and God the Holy Ghost, that already seemed like far too much complexity for one myth and there were still two pages to go before we even reached the bit where Zeus concealed his daughter in his head and thereby retained the supremacy of the world.

It was only as I walked down to the cul–de–sac to Marina's house that I realised I had a sort of excuse for my mythic ignorance. Catholics just don't get taught myths. I can't remember a single time during my twelve years of schooling by assorted priests and brothers when Zeus got a solitary name check, let alone Hestia, Demeter and Hera. There were no doubt good theological reasons for such systematic neglect. People who are intent upon indoctrinating children into the myths of Christianity are hardly going to spend any time drawing attention to the religion's relativity by allowing their audience to draw any sort of parallels between God the Father and the Olympian Zeus, let alone between the virgin birth and Athena, the goddess of wisdom, being ripped from her mother's womb.

There was only one problem with that excuse. Marina Warner was herself brought up a strict Catholic. And any idea that such an upbringing imprisoned her within the doctrine was brutally dispelled by her very first scholarly book, the compelling feminist reading of Mariolatory, Alone of All Her Sex: The Myth and Cult of the Virgin Mary.

Even before I'd finished the slice of treacle sponge and strong coffee which she'd generously set out for me, I was busily trying to discover how she managed to move so quickly from what must have been a powerful subjective belief in Our Lady and all her works to a thoroughly academic assessment of the cult's deleterious impact upon images of the female and feminine.

I reminded her of the book's opening lines: "Invocations to the Virgin Mary marked out the days of my childhood in bells; her feast days gave a rhythm to the year; an eternal ideal of moral beauty was fixed by the lineaments of her face, which gazed from every wall and niche."

"Oh yes, I remember that sort of belief very acutely. In fact I've only just grown out of envying people who still have it. For a long time after I'd written that book I still felt I wanted to be associated with people who had such faith. They had a line to something I had severed, to something that gave you consolation. The Virgin Mary is after all the mother of mercy. She is the one who allows you to be a sinner and yet still be taken back under protection, under her mantle. She will forgive you and intercede for you, and get the great judge to be kind to you. I still mind it a bit that I exiled myself from that possibility of redemption."

I told her I was still puzzled. How could such sensory and aesthetic and moral indoctrination have been so readily overthrown? How precisely did she lose her faith? What was the critical biographical moment? "I really don't remember what triggered it. Well, yes I do. We used to have retreats at school with Jesuits, and I put a question to one of them and he didn't give me an answer." What did she ask? Was she perhaps puzzled as many children are by the virgin birth. One teacher at my Christian Brothers school used to get over the twin problem of conception and birth by speaking of 'two way virginity'. Or had she, like Graham Greene, found it difficult to accept the idea that Our Lady and her physical body were 'assumed' directly into Heaven? I was, it seemed, being far too literal, far too simple–minded.

"No. Neither of those. I wanted to ask why Christ had to be sacrificed in such a bloody manner. I think I had Buddhist intuitions at the time and I wanted to be saved by something more serene. Actually, I haven't changed my position on that. My objection is to the idea of redemption in which a jealous, powerful, angry God kills his own child. That's one of my chief quarrels with that form of Christianity. For a religion of love it seems so dreadfully abhorrent."

It's that way of talking — whether in her writing or her broadcasts — which has always made me admire Marina Warner. I love her magnificent assurance, the manner in which she can casually pick up one of the world's great religions, inspect it for a while, compare it carefully with other related myths, detect a critical failing, and then proceed to dismiss it as somewhat unsatisfactory. It reminds me so much of one of the stepping stones towards my own loss of faith, the teenage moment when I found a sentence in Aldous Huxley's Point Counterpoint in which one of the leading characters cites Jesus as nothing more than an example. "Yes," he says — I'm paraphrasing — "But surely the same argument could be made for a whole range of moral philosophers, for Plato, Aristotle, Jesus, Hegel or Nietzsche." What could be more daring, more arrogant, more, well, Olympian, than to sentence the one and only Jesus to a mere place in a list?

It's quite unfair, though, to imply that Warner is an arrogant person or that she is in any way contemptuous of the myths she criticises. She doesn't cite imperfections in the Christian story in order to dismiss it from sight: she constantly refers to the impact that story still has on her life. You might say that her aim was modestly remedial. The Virgin Mary could be tolerated for her merciful, loving, consolatory virtues if only one didn't at the same time have to buy into her passivity and sexual repressiveness. Myths as such are not reactionary. But they can have reactionary elements. They can go off the rails. They can get pushed or pulled in the wrong direction. She feels, for example, particularly strongly about the role that Saint Augustine played in the road taken by the Christian story.

"Augustine really was a wonderful man. He was an extraordinary writer, a fascinating, profound character. So it was a terrible step when he took the church in the wrong direction, when he adopted the idea that we are all originally tainted by concupiscent sexuality. That has taken us in a terrible direction. Just imagine if Augustine had said that we were tainted by our capacity to murder one another and that this was what we had to be redeemed from. Then we would all have had to concentrate upon dealing with hate and bloodthirstiness instead of pouring all our energy into controlling sexuality."

This is a nice example of the ambivalence towards myths that runs through so much of her work, whether she's writing about fairy tales (From the Beast to the Blonde), or on mythical stories with their origins in reality (Joan of Arc: The Image of Female Heroism) or on the history of the male demon (No Go the Bogeyman). In one way she's happy to accept that myths can be bad for us, to agree with Roland Barthes, that they are examples of 'depoliticised speech', ways of persuading us that something which is in fact highly ideological, highly partisan, highly historical, is really only a matter of universal common sense. (One of the clearest examples of what Barthes meant by this appears in an essay called 'The Great Family of Man' in which he visits an exhibition of photographs devoted to showing how the peoples of the world deal with such universal matters as birth, death, work and play. This is all presented as utterly uncontentious. We are simply, asserts the prospectus, being shown pictures of the human condition. But, says Barthes, this is really a myth we are being sold, in that such an exhibition denies difference; differences in work conditions and wages, differences in infant mortality rates and life expectancy (he might have added that the very title of the exhibition also denies gender difference). The radical theorist's proper task is to destroy the neutrality of the exhibition, to demythologise it.)

Warner is happy to accept this version of myth.

"I think that Barthes was completely right and everything he said is completely relevant to the contemporary world of communications and ideologies. And yes, one has to be vigilant in the way that he suggested and try to spot falsehoods, examples of mythmaking in the stories that people tell about the world. And I would say that there is an element of my work which is de–mythologising. I know the dangers of myths. I know why myths were so important to the Nazis. I know that the Holy Grail was some kind of Nazi myth. I know the importance of uncoupling the story from the reality."

I suggest there's a big 'but' on the horizon.

"There is. I have also become associated in people's minds with being a proponent of myth. And that is the other side of me. You've got it out of me already. All that stuff about the Virgin Mary, all the festive pageantry of myth. I simply love the stories. I can't resist the stories."

I asked her if it was true, as I'd read somewhere, that she still went in search of long forgotten saints merely so that she could add yet another story to her collection.

"That's right. I have just written about Saint Frideswide. She is the patron saint of Oxford. She is an example of the classic virgin martyr story in that she was pursued by lustful suitors that she didn't want and she struck them all blind and fled to Binsey where there is a holy well; the holy well is the treacle well in Alice in Wonderland and the treacle in the well which figures in Alice in Wonderland is Saint Frideswide's treacle, a balm for the eyes that cures blindness."

"I love the stories but I know that I have to be terribly vigilant about what they're saying. In some cases, of course, they're telling us something that would otherwise be hidden. My work on fairy tales was about that. About how overlooked categories like fairy tales could contain cells of female power, could provide space for female infiltrators. In fairy tales you can discover how women were oppressed by the dowry system, by the arranged marriage system, by their lack of education, by the lack of control they had over money. All those themes are in fairy tales. Fairy tales are about money, marriage and men. They are maps and manuals that are passed down from mothers and grandmothers to help them to survive."

This, I suggest, isn't just a modification of Barthes, it's a full–scale rebuttal. In books like From the Beast to the Blonde and Monuments and Maidens (in which she reflects on the manner in which so many statues in western cities use female figures as embodiments of abstract principles like Liberty and Justice) she was surely not so much de–mythologising as rescuing that which was properly female from its narrative or marble prison. And women were particularly implicated in such mythical rescue operations because they were much more likely to be imprisoned by myth. That was surely also the name of the game in Joan of Arc, where she was trying to get back to the real historical figure and scrape away the narrow set of mythical categories that were reserved for the depiction of unusual 'unwomanly' women.

"I think that's right. And a lot of work has been done on that in other areas by feminist writers. In music and in art and in history. But I think in a sense that this is an enterprise that now needs to be taken up for men. I know it's a bit of a cliché to say that nowadays it's the men who are suffering but we do need a way of providing young adolescents with more possibilities than they now encounter. Lad–lit is very narrow in its conception of young men's possibilities."

But wasn't this to talk of myth as potentially liberating, to argue that we need better myths than those that currently dominate our politics and culture?

"Yes. I am about to go to New Zealand to give a lecture on that very subject. My theme is the triumph of the Book of Revelations in our culture. The idea of the impending cataclysm, the final cataclysm of the Beast being struck down, the day when the seven seals are opened and the brimstone comes pouring down on us. That is the message that is now being thundered from pulpits in the mid–west of America and through tele–evangelism. And, of course, that evangelism has spread through Africa and Latin America. Great Catholic strongholds now have vast communities of evangelical apocalyptic people within them. There is something in the human imagination that loves nothing more than to imagine the defeat of the enemy. It's another example of the terrible consequences of Christianity taking a false turning. A false turning that didn't have to occur. Because the Book of Revelations only just got into the Bible. Scholars sat around conversing learnedly on what should be in the canon, and it only just squeaked in at the very last minute. If only it was an heretical book then we would not be in so much trouble."

Once again I find that my head is filled by a picture of Marina Warner seated at this or that learned table and patiently arguing with theologians about the consequences for humanity if their 'myth' goes in one direction rather than another. It's too late now for her to have any say in Saint Augustine's turn away from love towards sex, or in the debate which led to the installation of the Book of Revelations in the Bible. But what has she to say about the secular myths of contemporary society? Is she happy with the stories that we now tell ourselves about how to find personal happiness and social justice?

"There have been two dominant stories. One, which began originally as a good idea, was the liberation of the individual, the notion of self–expression and self–fulfilment that was at the core of the Enlightenment. The idea that every individual had this great store of personal ability. Now, that unfortunately has become uncoupled from the other story about society as a mutual enterprise and has degenerated into what was called the 'me generation'. But as Hobsbawm has said, the world will not get better on its own. It is one thing to have the empowered individual but that should not replace the idea of mutuality, our need to live in colonies, to be ants rather than tigers."

I suggest that she might use her great talents to invent a new myth, one which might incorporate a more complex set of ideas than the current stories of imminent cataclysm and the Manichean fight between good and evil and the wonders of self–discovery.

"I would love to do that but I think it is rather beyond me. When I write fiction I do think of my words as creating acts, the idea that words generate things in the world. This might sound a bit crackpot but I do actually believe that language institutes reality in some mysterious way. So that, if you have good laws, well written laws, you can generate the justice that the words of the law have imagined. So laws shouldn't only be defensive and protective, they should have an inaugural sense of what we want. They should have a sense within the language. And that is why the constitution of America, despite some awful clauses, is good, because it is informed by the idea that you can inaugurate justice by speaking it. Toni Morrison says about one of her characters: 'I wanted a language that wished him well.' This is not a good character she's talking about. He is a murderer. But she wants to use language to wish him well. And that is what I wanted to do for refugees in my last novel, Leto. I wanted readers to feel sympathy with this sort of asylum seeker, this ordinary person, a mother with two children who stole and did a bit of part–time prostitution to keep herself alive. I wanted to wish her well. I wanted readers to feel sympathy for her."

Marina Warner may have a deliciously intelligent ambivalence about the nature of myths but throughout her life she has unequivocally been on the side of creative and cultural diversity. She has tried ceaselessly to rescue us from the falsehoods and banalities of some of the myths that inform our lives, while simultaneously showing how myths can often help us to discover truths about the nature of personal and social identity which might otherwise go unspoken. "In her vision," wrote one recent commentator upon her work, "stories confirm a community of imagination by celebrating the individuality — the strangeness, the wonder — of life. It is thanks to writers like her that we can still believe in the power of myth, metaphor and metamorphosis to present us with the possibility of 'other worlds'." (Marina Warner by Laurence Coupe, to be published by Northcote House).

My long, intense conversation with her certainly had a strange disorientating effect. Fifteen minutes after leaving her house I realised that I was getting no nearer to Kentish Town Road and the tube station. I had been walking round and round in circles. Who could I find to help me back on the straight and narrow? Every new street I turned down was completely deserted. After three more fruitless turns I spotted a motorcyclist at a crossroads. I raced over before he could accelerate away and opened my mouth to ask for directions. But he beat me to the punch. "You still trying to find your way out of here?" he asked. I peered into the goggled face and realised it was Guy, our photographer, who had been with me in Marina's front room for the last hour. "Yes," I said, "I'm completely lost". "So am I," he replied.