PETE, dressed in a multi-coloured jacket, was waiting for us in a quiet country pub. He was to be our guide to the party. A few pints and a brief car trip along the Wiltshire lanes later, we parked in a field next to an old blue and white Fifties bus, and walked through the waist-high grass towards the sound of music.

As the temperature rises, the nights become warm and dawn is early, so sound systems find their way into fields, and people leap tirelessly from one foot to another in the grass. The rave season is here again.

But this year could be the last. The proposed amendment to Clause 39 of the Public Order Act will redefine criminal trespass, entitling police to confiscate equipment and break up convoys or gatherings of 10 or more.

Near Longleat on Saturday the ravers did their best. By about two in the morning the police had set up road- blocks at the top of the hill to halt anyone attempting to leave or enter the site. But the flashing blue lights gave their position away and the organisers spent the rest of the evening alerting punters and redirecting the traffic around the road-block.

The music thumped into the night, and around half of the 2,000 dancers set up tents, planning for a long stay. A small cardboard sign on the fence - 'invitation only' - sufficed to prevent the police from breaking up the event.

The movement has been slow to kick into gear this year, with little happening over the last bank holiday weekend. The police have stepped up their surveillance operations: there are intelligence units in Devizes, Wiltshire, covering 26 southern forces, and in Penrith, Cumbria, covering 17 in the north.

In March, Operation Snapshot established the numbers and precise whereabouts of New Age travellers. Groups of travellers all over the country were dispersed over the last bank holiday, courtesy of pounds 500,000 from the taxpayer.

'A lot of the people I know and the main members of the group have gone abroad for the summer,' said an ex-member of Spiral Tribe, the group which organised Castlemorton Common. On that occasion 25,000 ravers took the Hereford and Worcester police by surprise with a week-long party spanning the Whitsun weekend last year.

'Some of the members are still awaiting trial after Castlemorton, and everyone else has had their sound systems confiscated. So there aren't many of us left, but those of us who are around are have moved into more legal stuff - we're hiring premises and going on tour like that. The free party scene is still going on with people like DIY, but I don't think that there will be another Castlemorton.

'But then again, anything could happen. As everyone knows everyone else on the scene, all you need is someone to say there's something on in South Wales, and that gets stopped, and you end up with something massive in Cornwall, as everyone has been moved on there. That's how Castlemorton started, with everyone being moved on from the Avon free festival.

'At this stage I would not rule out anything, as this is the last time anything like this can really take place. With the introduction of the Clause 39 amendement, people have a sense of the last stand.' He laughed. 'I mean, who would have thought that it was easier to dance in France and Spain? I thought we were supposed to be a free country.'

A healer with waist-length dreadlocks who played the didgeridoo at Castlemorton last year said that the rave movement had more or less divided into those who were genuine travellers, and those who were weekenders out for a bit of confrontation. He had been staying away from illegal sites, he said, preferring to go to organised events to avoid hassle. He had just come back from an Earth Spirit healing festival in Sussex.

The movement now, he said, 'has changed to a more eco-level, which is just as subversive. It's transmuting into a movement that is much more to do with basic human rights than music. There is a growing awareness in people's minds that will build up over the summer and end in a large confrontation, because they believe that this a form of social cleansing. The new laws are marginalising a certain group of people without acknowledging their needs, and making them a race unto themselves.'

A sound engineer from a group that also played at Castlemorton believes that the expense of this year's Glastonbury Festival ( pounds 56 a ticket) and the strict no-travellers policy, coupled with the heavy policing of Stonehenge, will cause extra friction. 'After Glastonbury and the big ones there will be a definite increase in activity, with the hard-core travellers causing as much chaos as they can. If they can get it together, of course.

'But when people are talking about 'us against them' it makes the magic disappear, and that is basically what it's all about - magic. It's got nothing to do with rip-off merchants who try to produce that effect through the pharmaceutical route. But it all depends on how much the police choose to enforce these new laws. I don't understand why they don't just give them a field and let them get on with it. It would cost a hell of a lot less in the long run.'