You probably don't spend a lot of time worrying about the end of the world. Why should you? Terrible events like Jonestown and Waco prove that all millenarian movements are dangerous, sinister brainwashing cults, and dozens of commentaries use failed predictions about the end of the world to show that such movements were just plain silly. ("Do you know how many times those Jehovah's Witnesses got it wrong?"). So I started to wonder how come millenarianism seems to be such a powerful religious force in the world. Why are millions turning away from established religions to evangelical creeds that talk readily and constantly about the coming apocalypse?

I began my quest with Abi Freeman, who is now one of the official spokespersons in Britain for The Family, the strongly millenarian movement which, under its former name, the Children of God, gained considerable notoriety for its adoption of the now-abandoned recruiting technique of 'flirty fishing' (a form of evangelising using sex). What I wanted from her was an answer to the question which is raised at the beginning of historian Damian Thompson's extraordinary book, Waiting for Antichrist: "How can people believe that the supernatural end of the world lies just around the corner when, so far, every such prediction has proved wrong?"

When we met up at a café down the road from London's Piccadilly, she smiled, brushed her disorderly hair away from her forehead, and told me that it was really no problem. "You only have to look around you. Look at all the signs. We're living in the period before Jesus will physically come back to earth. We believe that because the Bible is full of countless and very specific prophecies. And virtually every book of the Bible has a prediction about the world going through this major change, which we call the Second Return of Jesus. I'm more convinced now than I ever was. Years ago, I was still learning, still reading the scriptures. But now every time I turn on the television and watch the news, it is like watching a movie that I know already. All the things that we are expecting to happen are happening. All the natural disasters. All the signs of suffering. All the dying from hunger and disease. It makes me say, 'Hurry up and come quickly, Jesus. The world's in a mess. Please hurry up'."

And you're sure he will come? "Oh yes. One of my favourite scriptures – it's in the Book of John – is where his disciples are all worrying and fretting and asking what is going to happen. And he says, 'Don't worry. I'm going to my father's house where there are many mansions and I'm going to prepare a place for you. I'm going to get it ready and I'm going to come back and take you there myself.' That's a paraphrase but that's what he said. He said, 'I'm coming back to take care of you.' He's a God of love. He loves everybody."

It is slightly chilling being in the presence of quite so much certainty. But there's also something rather stimulating about having a conversation with someone whose days are never punctuated by ambiguity, doubt or ambivalence, who knows to the core of her being that she has found the Truth.

She's so happy to argue vigorously for her beliefs that never for a moment does it occur to me, as it has to so many partisan writers on new religious movements, that she might have been seduced or brain-washed into her present credo. Nor do I ever think that she might be slightly mad or have lost her capacity to reason. From time to time she even laughs aloud at my thoroughgoing scepticism – she knew all about my views well before she agreed to travel from Crewe to London to talk to me – and is perfectly alive to the oddity of talking about the coming apocalypse while people around us are busy drinking coffee and eating egg on toast. Neither does she mind her beliefs being attacked. She stoically explains that this was how life was always going to be for those like herself who subscribed to a religion that was not reserved for church on Sunday but that had an impact on everything she did and made sense of nearly every aspect of her life.

Abi's theology takes many of its key elements and predictions not merely from the scriptures but also from a quasi-sociological analysis of trends in politics and science. She tells me that one sure sign of the imminent end of the world is economic and political globalisation and in particular the emergence of a world government dominated by a single dictator. This development, she argues, is an inevitable consequence of humanity surrendering to capitalist values whilst at the same time following the lead of celebrity culture and placing its trust in one charismatic individual.

It's at this point in our conversation that I begin to recognise that while there are plenty of elements of Abi's faith which seem silly or even ridiculous when examined in isolation, there is still a sort of controlled logic to her argument. She displays what Damian Thompson neatly calls "subjective rationality", a rationality that "combines elements of logic with a whole range of factors: personal taste and convictions, limits of the available information, the circumstances of the moment." She is, in other words, using conventional mental procedures for weighing evidence. But, of course, where she departs from customary rationality is in the primacy she accords to scriptural prophecy. I ask her what the world government she's been describing would look like.

"According to Chapter 13 of the Book of Revelation it has such vast control over mankind that nobody can buy or sell if they haven't bought into their system. They accept some mark, some form of identification, to show that they are yielding to the control of this one-world empire."

I realise that I am now on a road of no return. I can only go with the flow. What sort of identification? And how could that become a form of control?

"Well, for the first time in history it is now technologically possible to have your identity printed on a smart card of some kind, an identity card or a credit card. Unless you have that card you can't get into places, you can't buy things. Now, those cards could be stolen so the only way to make them foolproof is to put them in you, to place a microchip underneath your skin so that you can simply be scanned whenever you wish to enter or leave anywhere. And once that chip is in you, and it's already happening in some parts of the world, it's in some sense controlling you. That could be the mark."

What mark? She plays her trump card. "It's what the Bible says. It is the mark of the beast. It's 666. And we must not take the mark of the beast. We must watch out for it."

But supposing this dictator is really the beast, the Antichrist. How will we know from his rule? When will he show his colours?

"At first everything will be benign, but in the middle of his seven-year reign, he will set himself up as a god and demand to be worshipped or rather demand more and more allegiance. He will lay claim to all other religions. And that's the point when true devout believers will rebel. Not only Christians. Many orthodox Jews and many Muslims will resist. At first it will look like the world government is winning. He's got the force on his side and the numbers of people. But then Jesus is going to come back and say, 'Look, you messed up so bad. You've messed up the environment. You've messed up individually and collectively. You've ruined the world. I gave you a wonderful world and you've completely messed it up. I'm here again to sort it out.' And then I believe the world will start again."

And all will then be well?

"That is the beginning of the 1000 years reign of Jesus on Earth, the time when Jesus and his believers will run the world. It will be a wonderful time. Wonderful."

When I press her for more details of this wonderful time, Abi becomes unusually reticent. She simply says again that it will be wonderful. I'm not too surprised. Damian Thompson has already told me that millenarians like Abi typically feel less interested in the features of the millennium that they're waiting for than in the circumstances that will give birth to it. Neither do most of them ever seem to make practical preparations for the end of the world that they so vividly announce. Very few start hoarding extra tins of baked beans or freezing loaves of bread for the day when the trumpet blows.

But Abi, in common with other subscribers to millenarian religious movements, is absolutely specific on one aspect of the future: she will find her paradise on this material earth. She is also certain that those like me who fail to recognise the signs of the end which lie all around them will be punished for their non-belief. They will, as prophesied in the Book of Revelation, have to endure such horrors as plagues, famine, poisoned water, hailstones mixed with blood, and flesh devouring birds.

I don't though get any sense that she is vindictive about the fate of non-believers. I've heard hard-line Catholics express more sadistic pleasure over the likely fate of Protestants in the next world than she does over the tribulations that lie in wait for sceptics when Jesus makes his dramatic return. But, as Damian Thompson explained to me, all millenarians necessarily believe that they will be spared. "There's not much point in believing strongly in the end of the world if you get nothing out of it." But as he also pointed out, the type of beliefs currently entertained by Abi were exactly the type of apocalyptic doctrines that originally informed many of our most established religions. "Nothing embarrasses an orthodox religion more than pointing out that they began by believing that the world was about to end. In the case of Christianity, churches have to negotiate the very difficult and awkward fact that Jesus himself implies very strongly that the world will end in the lifetime of his listeners. So churches have to say to themselves: 'Did Jesus get it wrong?'"

But surely orthodox religions never subscribed to the coded prophecies in the Book of Revelation that seemed to underpin so many of Abi's assertions? "Well, I agree that the Book is very cryptic, very numerological, and very difficult to read by what you might call the unenlightened. But it's quite disturbing for mainstream Christian scholars to realise that the Book of Revelation, with all its terrifying and homicidal imagery, was probably more important to the early Christians than the gospels themselves."

The Book's emphasis on the symbolism of numbers could still be discerned today in the most unexpected places. "I remember when all this came to a head in the year 2000 when Pope John Paul II who had quite an apocalyptic streak began to issue, not exactly prophecies, but interpretations of the year 2000 which didn't involve the end of the world, but nevertheless assigned tremendous spiritual significance to the dawning of the new millennium. The cardinals and bishops didn't want to know. And it was the same with the Church of England, which is why they didn't have a bloody clue about what to do with the Faith Zone in the Millennium Dome. They should have handed it over to the Pentecostals. They could have done something with it."

After I'd talked to Abi I went on to meet members of other millenarian movements. I had lunch in Fulham with believers from the Etherian Society who believe that the end of this world will be marked by the return of Christ from cosmic space, and squatted in the kitchen of an Elephant and Castle council flat to learn from a Rastafarian about how the Asian tsunami was a punishment for the wicked. I sat in the back of a black cab and discussed the exact time and date of the arrival of the third Mahdi with a devout Muslim, and travelled to a Catholic seminary in Cockfosters to meet an eminent Catholic priest who believed that his church had been foolishly led to play down the imminent end of the world because of its fear of being associated with extreme religious cults. In all these conversations I was struck by the manner in which such believers linked their worries to real events in the world. They all spoke with confidence and knowledge about the threats posed by global warming and viral epidemics and the possibility of terrorists obtaining nuclear weapons.

There was nothing sinister or silly or mad about any of their pronouncements. Their stories of the way the world would end were no more irrational than the more familiar stories from orthodox religionists about the resurrection or the virgin birth. Sometimes their views about the manner in which non-believers would be punished were indeed disturbing but there were also times when it was my own easy-going optimism that came under challenge.

"Did you say you were a sceptic?", asked one young man who'd been busily telling me about the nature of Armageddon. "How can you look at what's happening in the world today and be sceptical about the idea that its days are numbered? You're the odd one out. I should be interviewing you."

Laurie Taylor's investigation into millenarian movements, A Very British Armageddon, was broadcast by Channel 5