Gotcha] 'Look at that Marauder 412 De Luxe swaying about - its owner should be made to take a road test,' roars Craig Bunty above the drone of the motorway.

Mr Bunty, a landscape gardener from Cheltenham, is on patrol with the Anti-Caravan Club (ACC) on an M5 flyover. Thirty feet below, the traffic is bumper to bumper across all six lanes. Newly- waxed caravans, fresh from suburban driveways, crawl along the slow lane in cream-coloured convoys: Jet Streams, Sprinters, Monzas, Elusions, Rapides, Lynx, Siroccos and Cyclones, misnamed descendants of their gypsy forebears, trundling towards the South-west. In their wake is a tailback of seething frustration as hundreds of families bound for summer holidays by the beach are reduced to crawling in a low gear.

'It's ridiculous,' shrieks Liz Batty, a textile designer from Gloucestershire, glaring over the railings at the congestion below. 'Caravans should be made to travel at night.'

The ACC regularly patrols the motorway in summer, monitoring and logging numbers, building up statistical data to add force to its campaign.

Its chairman and founder is John Williams, a marquee contractor from the Cotswolds, who felt driven to set up the group while travelling to a Highland ball on the A87 from Invergarry to Kyle of Lochalsh. 'With no opportunity to overtake, we had to plod behind a beige Comtesse for nigh on 30 miles. We were very late.'

Two years later, the club has 840 members and has so far received only one hostile communication: a cut-out card of a caravan bearing the message: 'You miserable bastard.' It is now planning to sponsor road signs at one-mile intervals: 'In a caravan jam? Be patient, 46 miles to Balmacara.'

'Sprite]' screams a small girl, peering through the steel railings on the bridge, logging it on a scrap of paper. Moments later, there comes a retaliatory cry of 'Swift]' from her nine-year-old brother.

'That's what happens,' shouts Mr Williams, scanning the fast lane with enormous ex-Navy binoculars and pointing towards a Ford Scorpio pulling a Monza, in which three children can be seen fighting on the rear seat. 'This is a stressful time for caravan owners.'

Mr Bunty nods sagely - he has an inbuilt grasp of the caravaner's psyche. His stepfather had a caravan permanently hitched to the family car for 17 years. 'It was embarrassing being taken to and collected from school every day towing this thing. People thought we were weird.'

It was not until Mr Bunty was 18 that he realised cars could go faster than 45mph. 'There's no doubt the old man enjoyed holding up the traffic. He often used to say, with perverse zeal: 'We may be the snail, but they are the slime.' '

After another two hours of logging, the patrol breaks for lunch. 'We have just notched a significant victory,' explains Mr Williams. 'Mandatory testing to tow a caravan will be introduced in July 1996. The current situation, where a 17- year-old can pass his test one day and be towing a 20ft caravan the next, will be a thing of the past.'

He quickly runs through some club news: the Dawn till Dusk Curfew, restricting caravan movements to night hours, is still the spearhead proposal, while spraying caravans parked on sites with organic slurry, to make them harmonise with the landscape, is being considered for the manifesto. 'Camouflage them,' suggests David Pritchard, a new recruit to the club, but Mr Williams points out that they would then be unsafe on the road.

'I am afraid some caravaners take us very personally,' says Liz Batty. 'They think the ACC is a fig-leaf for a bunch of snobby motorists who want any obstacles in their path removed. In fact we just want to highlight the issues and debate them sensibly.'

'Caravaners get a lot stick from sales reps,' says Mr Bunty, gnawing a chicken leg. 'They joke about them being the mobile equivalent of anoraks.'

'Anoraks?' asks a bemused Mr Pritchard.

'Train spotters,' explains Mr Bunty. 'Skoda drivers have been the fall guys of the road for so long, they need a new target.'

Mr Williams then unveils an addition to the club manifesto. 'It's called the Caravan 5 hand signal,' he says, demonstrating the movement by spreading his fingers and thrusting out his right arm. 'The idea is for an oncoming driver to use the signal to alert caravan owners that five vehicles or more have built up behind them. The towing vehicle is then obliged to halt at the first available opportunity to let the vehicles pass.'

A short distance away from the patrol's picnic, behind a screen of wind-scorched pines, some caravaners have congregated under a haze of diesel fumes in the the coach park of a service station.

'Anti-Caravan Club? No, I have never heard of them,' says Margaret Ashton, from Newbury, Berkshire, framed by the doorway of her Musketeer. 'For goodness' sake, whatever next? There will be an Anti-Existence Club before long]'

'You've got to take a break,' says David White, from Sheffield, lowering the front wheel of his Pioneer and pointing towards the distant drone of the M5. 'It's murder out there.'

Inside, his wife and three children sit around a table fanning themselves with puzzle books. 'Travel at night? Ridiculous] What would you do with the nippers?' he says, checking that his rear jacks are grounded.

Guy Baker, a textile wholesaler from Caterham, Surrey, is unimpressed by the Caravan 5 signal. 'What's stopping any old person doing it for a laugh? Anyway, if you are pulling a caravan you should know what you have got up your jacksy.'

At Trevedra Farm Caravan Site, near Land's End, the ACC's proposals are not only received with tolerance but, surprisingly, with some agreement. 'We always travelled at night anyway,' says Hazel Jones. 'We used to carry the kids to the car asleep in dressing gowns and put them in the back. It was an adventure.'

John Wood, a policeman from Looe, Cornwall, offers another view: 'They are 25 years too late. The traffic is so thick now that if you are stationary in a three-mile queue it doesn't matter whether there is a caravan in front of you or a bicycle. It would be nice to see one of the political parties come up with a viable transport policy. They know full well things are getting worse, but each are hoping that when the crunch comes they won't be in power.'

'Compulsory testing for caravan pullers is a good idea,' says Shirley Wood, 'and teaching people how to load them safely.' 'Mind you,' adds her husband, 'with today's roads, as long as you can point a car in the right direction you shouldn't have any problems.'

As the scent of heather floats down from the Penwith moorland, the conversation takes an environmental turn. 'Tourism is the only industry in the area,' says Mr Wood. 'You want to attract people, but at the same time protect what it is they are coming to see. We live by the sea in Looe, where there are thousands and thousands of static caravans. I would say it was saturated. But I had a friend in Looe who was a councillor and businessman. He said: 'If I could flatten everything and make it into a big caravan park and get more people in it, I would.' '

This is a sentiment that would horrify the Anti-Caravan Club, whose day on the flyover has taken a dramatic and unexpected turn. The weight of traffic, so gleefully monitored by the patrol earlier, has reduced dramatically, and there is barely a caravan to be seen. Training his binoculars towards the Midlands, John Williams ignores the grumbling that has broken out between the bored children. 'This is fantastic,' he says. 'The curfew idea is obviously kicking in. Soon we'll have to organise a night patrol.'

(Photographs omitted)