Delgado was gazing at a large area where the crops had been mysteriously flattened in a remarkable pattern. A large, nearly perfect circle of plants had been bent down in a clockwise direction. Extending from the circle were other shapes: antennae, a ladder-like strip and a semicircle.

The Sevenoaks phenomenon is the latest of hundreds of circular patterns that have appeared in the grainfields of southern England and, in lesser numbers, in the fields of 20 other countries during the past 13 years. And it seemed perfect fodder for Delgado, who now makes a career of investigating and writing about the circles. He has suggested that the circular patterns are created by a "superior intelligence" - most likely extraterrestrial and has co-authored a book called Circular Evidence with another believer, Colin Andrews. It has sold more than 50,000 copies.

Delgado's exultation was soon cut short. Graham Brough, a reporter from the London tabloid Today who had alerted Delgado to the latest apparition, introduced him to two land-scape painters, David Chorley, 62, and Douglas Bower, 67. They had created the Sevenoaks circle while Brough looked on. Moreover, the duo revealed , that for the past 13 years they have been sneaking around southern England at night, fashioning as many as 25 to 30 new circles each growing season. Their efforts apparently inspired copycats, who in the past decade have used a variety of techniques to shape hundreds of crop circles both in Britain and abroad. Said Bower to Delgado: "I'm afraid we've been having you on."

Delgado was crestfallen. "We have all been conned," he admitted. "If everything you say is true, I'll look the fool." Indeed.

The admission brought an end to one of the most popular mysteries Britain - and the world - has witnessed in years. Flying saucers, out of vogue for sometime, were given new life by the whorls. Saucer enthusiasts argued that the cropland patterns marked the landing spots of UFOS bearing visitors from space. Believers in the paranormal claimed the circles radiated mysterious energy forces. The patterns spawned a kind of intellectual cottage industry: no fewer than 35 Britons claim to be experts on the phenomenon.

A new scientific discipline, cereology, emerged. It is practiced by members of the Circles Effect Research Unit, a privately funded group headed by Wiltshire-based physicist Terence Meaden. The group argued that a still unverified weather phenomenon is often responsible for the weird damage. It occurs, Meaden says, when whirling columns of air pick up electrically charged matter, flatten the crops below and produce the bright lights observers say they have seen above the circles.

Not to be outdone, a team of Japanese scientists, led by physicist Yoshi-Hiko Ohtsuki, had joined the hunt for an explanation. Ohtsuki believes a form of ball lightning generated by microwaves in the atmosphere flattened the crops; he created croplike circular patterns both in the laboratory and on a computer programmed to simulate ball lightning. Impressed by Ohtsuki's work, the authoritative British journal Nature published his report, leading the usually judicious Economist to suggest that the mystery might have been solved.

The hoaxers' technique required no meteorological effects and only rudimentary physics. After making a scale drawing of the intended pattern, Chorley and Bower proceeded to the wheatfield with their equipment: a 4-ft. long wooden plank, a ball of string and a baseball cap with wire threaded through the visor as a sighting device. At the center of the intended site, Bower held one end of the string. The other end was attached to the plank, held horizontally at knee level by Chorley as he circled around Bower, pushing the grain gently forward. "The heavy heads of the wheat tend to keep it down," he explained.

Chorley and Bower say they conceived their hoax in 1978, while sitting in a pub near Cheesefoot Head "wondering what we could do for a bit of a laugh." Inspired by reports of flying-saucer sightings, and recalling crop circles created with tractors by Australian farmers several years earlier, they decided to flatten some corn to make it appear that a UFO had landed. To their chagrin, this and other forays during the next three years went unnoticed. But one of their circles was spotted in 1981, reported in the press and promptly attributed to extraterrestrials. "We laughed so much that time," recalls Chorley, "we had to stop the car because Doug was in stitches so much he couldn't drive." It was only after circle enthusiasts began seeking government funding that the two jovial con men decided to admit to the hoax.