Crop circles are on the agenda again with today's opening of the film Signs.

The debate rages about how they are made and the waters are muddied still further by a new book that describes many of the images found in Wiltshire fields as being a form of mathematical genius.

SHIRLEY MATHIAS reports

IT was only a question of time before Hollywood got in on the act and a hero played by a movie superstar threw his twopennyworth of speculation into the corn circles debate.

In the movie Signs, which opens in Swindon this week, Mel Gibson plays a pastor and father of two who becomes a farmer after his faith in God is rocked by the death of his wife and is shaken to his roots when a crop circle appears overnight in one of his fields.

Divine intervention? Aliens? The rest of the film is taken up by a search for the answer.

But the pastor-farmer and his kids would not have been so gobsmacked if the script writers had set their farm in Wiltshire instead of the United States. We're used to crop circles around here. They have appeared in the county every summer for at least 20 years.

Now a new book by Nick Kollerstrom, a research fellow at London University, suggests we should be less concerned with possible alien influences and concentrate instead on the genius that goes into their designs.

In Crop Circles The Hidden Form he talks about their "amazingly subtle and beautiful patterns".

And he points out that they incorporate complex geometric forms and mathematical sequences. Here, in the corn circle capital of the world, we have seen asteroid and diamond shapes, heptagons, hexagons, pentagons, pentagrams, snowflakes, triangles, spirals and stars.

They have contained Euclidean principles devised by the Greek mathematician who lived 2,300 years ago, and the designs are becoming steadily more complex each year.

He talks, for instance, about binary fission in a circle that appeared at Stanton St Bernard last summer. About the triune mandala a triangle within a double hexagon at Silbury Hill in June 2000, and the nest of pentagrams which materialised near the same spot just weeks later. In June 1997 the Harlequin, a hypermathematical image involving a triangle and ten circles of six different radii, appeared at Winterbourne Bassett.

It is all way beyond most of us, unless we happen to have an A grade at A-level maths.

But Mr Kollerstrom's theories make sense when you look at the photographs.

You will be disappointed, however, if you hope to find conclusive evidence of who constructs these apparitions at the dead of a midsummer night.

When pressed, he would go only as far as to say: "I don't think many of the circles in my book were man-made. They don't show signs of being man-made."

Writing about the Ninefold Star which was seen at Cherhill in June 1999 he concludes that the circle-makers whoever they were had apparently linked the number nine to the nine moons of gestation. In other words to the 266 days between conception and the average birth.

And an architect, Robin Heath, told him: "If I had 10 surveyors working for me I wouldn't be able to make that in a field in one night."

So the mystery remains.

One thing is clear, however, from Nick Koller-strom's book: if the corn circle creators are hoaxers they must all be brilliant mathematicians with the power to levitate themselves above field level.