One of Hollywood's oddest acts of veneration will take place in a tiny London cinema on Tuesday when Disney hosts a private screening of its latest blockbuster for an obscure landscape gardener and his friends.

The party will watch Signs , one of America's biggest summer attractions, ahead of its release in Britain on 13 September. The film, made by Sixth Sense director M. Night Shyamalan, tells the story of a disillusioned minister, played by Mel Gibson, who discovers that aliens are carving pictures on his back lawn.

The subject should bring a warm glow to its guest of honour, Douglas Bower, the gardener who first invented that peculiarly British art form, the crop circle. 'There would be no Signs had it not been for Doug Bower flattening patterns in fields, and for the rest of us who have followed up his work,' said John Lundberg, of Circlemakers, the creators of Britain's best circles. 'That is why Disney agreed to this special showing.'

In short, crop circles are back with a bang. Having faded from view during last year's foot-and-mouth epidemic, those strange spirals and patterns that have peppered our fields every summer for the past two decades are flourishing again.

Last week one of the most complex yet created - a 100-yard-long image of an alien carrying a disc - appeared at Vale Farm in Sparsholt, Hampshire. Cerealogists, that is 'experts' who claim circles may have mysterious, possibly extraterrestrial origins, say the disc carries messages from another world.

Circlemakers' Rob Irving believes otherwise. 'It's a classic late-season crop circle. As the nights get longer, we have more time to work unseen in the dark, so we can create increasingly complicated designs. That is why crop circles are always best in late August. It's the height of the season.'

And from the Vale Farm example, it is clear these creations have reached new heights. 'We have certainly got this down to a fine art,' added Irving. 'Effectively, we are creating half-tone blocks in fields. Some people think this complexity proves aliens are responsible. If so, you have to wonder why they should do so using an artifact that went out with print unions.'

Not that this matters to the American visitors who are flocking to Britain in the wake of the success of Signs . Thousands have booked bus trips, particularly in Wiltshire and Hampshire, over the past few weeks. As one excited visitor told the BBC after seeing her first circle in the Vale of Pewsey: 'It's pretty trippy.'

Crop circles have clearly come a long way since 1978, when Bower and his mate David Chorley, who died in 1997, dreamed up the idea of fashioning enigmatic patches of flattened crops after a night at the Percy Hobbs pub in Winchester. Using a 5ft iron bar and a length of rope they marked out their first circle, and continued - with added refinements - for years.

By the early 1990s, with experts postulating that the circles were caused by twisting wind vortexes or 'mind energy fields', the pair were at the height of their powers. Farmers, originally enraged about crop damage, made thousands of pounds by charging entrance fees to their fields.

'It was just pure enjoyment,' Bower once recalled. 'Those beautiful summer nights for two artistic people under the stars amid all those cornfields.'

Their antics came to an end when Bower's wife Ilene grew suspicious of the mileage he ran up on Friday nights, and he was forced to confess to her and later to the media. But this had little effect on the fanatics, who remain convinced that crop circles have alien origins.

'It does seem odd that some people still think crop circles are made by aliens,' admitted David Sutton, of the Fortean Times . 'It was originally done as a prank, but now has become a valid form of land art, like white horses carved in chalk downs. It is a very British type of artistic expression. We should be proud of it - and of Doug Bower.'