So if we're in the grip of al fresco sex madness, where have all the lovers gone?

Britain's public spaces are said to be overrun with thrill-seeking exhibitionists. Our man put the claims to the test

After an hour of hanging around the park, success. A pair of lovers, swaying about out in the open for anyone to see. No shame. I started to get excited. And then the swans rose high in the air and flapped off in the direction of Walthamstow. Phwoarrr!

After an hour of hanging around the park, success. A pair of lovers, swaying about out in the open for anyone to see. No shame. I started to get excited. And then the swans rose high in the air and flapped off in the direction of Walthamstow. Phwoarrr!

Alfresco sex is not just for the birds, though. Britain, one senior academic will tell a conference this week, is in the grip of a frenzy for pre-arranged exhibitionist group intercourse with strangers in public places.

Dogging, as it is called, hit the headlines a couple of years ago when the former England footballer Stan Collymore confessed to meeting strangers in a car park. Cue sniggers and reflections that there are a few strange folk in the world.

But now it seems there are actually an awful lot of them. Dogging is suddenly being taken very seriously.

Dr Richard Byrne, an environmental affairs expert, will tell a conference of water and environment professionals in Wakefield that the nation's public spaces have become venues for hundreds of thousands of Britons to sate their lusts.

"From a study we did 18 months ago we reckon about 60 per cent of the country parks are affected by dogging," says Dr Byrne. "We have noted between 800 and 900 sites."

Doggers - the term comes from the voyeurs' alibi that they are merely taking a dog for a walk - meet up through websites, internet chatrooms and text messaging. Venues are identified, appraised, days and times chosen, sexual preferences stated. Dozens of specialist websites have sprung up in the two years since the dogging "phenomenon" first broke cover.

Assessing how many people are doggers, as opposed to internet voyeurs, is difficult. Tens of thousands have registered with dogging chatrooms in the past two years. One site recorded more than 50,000 readers last week for an advice message about personal safety in just 24 hours, and most are single, hopeful males. Far from being furtive, many websites are bullishly patriotic. "It is definitely British," says another. "It does not happen anywhere else in the world."

Venues range from lay-bys to supermarket car parks, gardens, river banks, motorway service stations and the most public of open spaces. "Though not as busy as in recent years," says one message about St James's Park, London, "there is still a reasonable amount of activity."

So is dogging really a growing social problem or an entertaining urban myth fuelled by cyberfantasists? I followed the advice of the dogging cognoscenti and made for Epping Forest, on the outskirts of London. Clutching a copy of the local newspaper and whistling a merry tune, I took up position around teatime on Friday - the most popular time, apparently, because doggers do it on their way home from work - beside Connaught Water lake.

There was a rustle. Two men and a woman, all together, all panting and sweating, just like the websites said. But not dogging. Jogging. On the far side of the lake a large man was sitting on a bench. Mentally undressing the coots in front of him, no doubt.

"In the 1970s, it was a voyeur-based activity - guys looking for courting couples," Dr Byrne had said. "You now have people with exhibitionist tendencies - people who want to be watched - doing things. The legal problems came when people started doing it in the day. That has become more of an issue in the past six to 12 months. There's more of a thrill factor."

Martin Whitfield, head forest keeper for the south of Epping Forest, was sceptical about a tidal wave of overt copulation sweeping across the land, or at least over his patch of it.

"I've been here eight years and indecency has been a problem, but not a major one," he said. "It stays in the same areas that I've always known it to be. If we catch people we deal with it, but they're well rehearsed in protecting themselves. They'll see us coming, and then disappear or stop. There is a park by-law offence which covers indecent use of the forest. We can use that."

Back at Connaught Water, I was getting a come-on from a coquettish magpie. By nightfall, the forest was silent, save for an occasional avian honk. As no doggers were making the beast with four backs - nor, for that matter, were any beasts - I beat a retreat, pursued by a cloud of midges. Gagging for it, they were.