Crop Circle
© Chris Jones
More than half the total number of crop circles observed throughout the world are found in the UK.
'Look, there's one with birds in it," I say excitedly into my microphone. Only as the helicopter whirrs closer do I see that the specks of colour dotting the shape in the cornfield below are not avian, but human figures in rainwear. Perhaps it is an angel with fanning wings, perhaps it is a cup and ball on a stick; the form is certainly new. Like all crop circles, it appeared, without warning or explanation, during the night; suddenly, this very morning, it was there.

The sun may have only just burst from behind the rain clouds to rake the tableland of the Marlborough Downs, but the people who have come to see these elaborate patterns are oblivious to the damp: they're lying down, head to head, their bodies radiating like the spokes of a wheel. The energies, I'm told, are still fresh. And we mustn't knock the rain. This month's bad weather has helped crop-circle aficionados by delaying the harvest.

Farmers in Wiltshire are wearily used to their corn being flattened into geometrical shapes. One of them has put an honesty box on top of an oil drum, in the hope that visitors will enable him to recoup some of the money he has lost from the crop. I notice that it is an old box. Crop circles are like truffles, mysterious but geographically specific, and they appear year after year.

We take off from a field near Alton Barnes, the centre of the phenomenon. Obviously the best vehicle for viewing crop circles would be a spaceship. But this helicopter, laid on as part of the Wiltshire Crop Circle Study Group's summer conference, which took place last weekend, is the next best thing, whisking me into a magical space where Silbury Hill looks like a suet pudding on a plate, and you spy on the gardens of manor houses that are invisible from the road.

The pilot's voice comes into my headphones. "There's one in front of us, shaped like a necklace." We bank over a landscape where the wheat fields are sheets of gold leaf. "The one to the left looks like a cross." I have the feeling that we are circling a cropped head - the football player Aaron Lennon's perhaps - with talismanic motifs shaved on to the scalp.

The archaeological features of this part of Britain are unique: only in southern England do you find white horses etched into hillsides, and there is no equivalent elsewhere to mysterious Silbury Hill. Crop circles are found in other parts of the globe, but not many. The 55 that have been spotted so far this year in Britain - mostly in Wessex - are more than half the total number observed throughout the world.

Today, the helicopter has been carrying people from all over Europe. Inspecting one of the circles on the ground - it looks far less decorative at eye level - I meet a couple of Dutch women. Dawn, who organises the flights for Fast Helicopters, says that they had some Norwegians last week, convinced the patterns were made by aliens. And what does she think? A diplomatic neutrality is adopted: flying crop-circle tours is good business.

To judge from the trade stands at the conference, crop circles occupy the same territory as leylines, shamanic drumming and the "global vibrational therapy"  of liquid crystals. Walking back from the tea tent, I see half a dozen people cautiously advancing with what I take to be cocktail sausages on long skewers held before them. They are would-be dowsers, learning the art of water divination.

Antoinette O'Connell from Ireland and Ana Vidal from Brazil speak about their experience of dragons, which manifested themselves quite suddenly to them, offering a means to heal the human race. "You don't tell anybody you are working with dragons," says O'Connell. "Your sanity could be questioned."

About a third of the conference delegates are healers. I don't know of many places where you can have your aura cleaned, but this is one of them. The conference opens with a period of meditation conducted by Francine Blake, a French Canadian, who founded the study group in 1997.

If you were expecting attendees to be dressed like fans of Star Trek, you'd be disappointed. There may be the occasional druidically long beard, but Blake is elegant and articulate. After years of study, her enthusiasm for the subject is undimmed. "It's the most exciting thing on the planet," she says during a break. "Science fiction for real."

Soil samples from beneath the circles that have been sent off for analysis in the States have apparently revealed traces of silica, suggesting exposure to intense heat - yet for so short a time that the crop does not burn up. Nevertheless, the wheat itself appears to be changed. Plant grain from a crop circle and it will grow taller and stronger than control samples, she insists, as though genetically modified.

It is widely believed in the crop-circle community that the shapes appear fully made, in a flash of light that illuminates the whole valley. "We don't know where the energy comes from," says Blake.

Jay Goldner, a jolly Austrian with a ponytail, whose bravura presentation wins a standing ovation with wolf whistles, thinks he does. The corn shapes are coded messages from the Creator, "a keyhole through which we can look into another dimension".

Ultimately, for reasons I did not quite follow but which have nothing to do with the London Olympics, he says they predict the Second Coming of Christ, expected to take place in 2012.

There is - whisper it if you dare - another possibility. Crop circles first appeared - or, as Blake would have it, were first noticed - in the Eighties. After a decade of speculation, during which it seemed that no human agency could be responsible for these miraculous designs, two men in their sixties stepped forward.Doug Bower and Dave Chorley claimed responsibility for a spectacular hoax, perpetrated not with sophisticated or extraterrestrial technology, but homespun equipment such as a plank and a length of rope. A baseball cap with a circle of wire attached to the visor provided a sight that could be aligned with an object on the horizon to keep the design steady. Case closed.

Well, not quite: certainly not to a community supported and reinforced by the internet and dedicated to finding alternative explanations. "We know that there are fakes," says the study group's bubbly administrator, Clare Oatley. "But as somebody said: 'Just because a faker can copy a van Gogh, doesn't mean that van Gogh didn't exist."'

Blake accepts that some crop circles are man-made, but they are very few. It simply takes too long. And when television crews and magazines try faking crop circles, they need ladders and lights. These things would be noticed, she says.

By the end of a morning, I find my resolute scepticism under strain. There are, I hear, people who camp out during the summer, hoping to spot a crop circle being formed. And yet, except for the person who started the flash of light theory, they never do. The designs are so complex, several individuals, surely, would have to team up to make these elaborate patterns. It may be that GPS, computers and infrared goggles have replaced the old baseball cap and bent wire, but how could so many crop circles be made so perfectly, each in a single night, without anyone being the wiser? Wouldn't someone have spilt the beans after one too many pints in the pub?

Certainly, the pleasure of making the crop circles must be so secret and nerdy as to make computer hackers, virus-writers and graffiti taggers look normal. One can take another view (unless, perhaps, one is a cereal farmer). "I have absolutely no idea how they get there," says Oatley. "I just like to enjoy them for the wonders that they are."