An illegal rave is being planned to cater for people shut out of the Glastonbury festival, BBC Radio Five Live has learned.
About 3,000 people went to a recent rave in Herefordshire
The event will be staged by the same people who put on a free party for a crowd of 3,000 on a farm near Leominster, Herefordshire, on Saturday.
At least 20 people were arrested after some revellers attacked police with bottles and set dogs on officers.
Many people who are expected to go to the Glastonbury rave are frustrated at having to pay more than £100 for official festival tickets, which sold out within 24 hours, organisers told Five Live.
The rave will take place from 21 June, the week before Glastonbury, Five Live said.
We'll have roadblocks miles back
Revellers will be sent the location by mobile phone text message.
One rave DJ told Five Live: "It's OK if you can get yourself a Glastonbury ticket at £100 within a couple of seconds because your dad's got the money.
"But some people have never had a credit card in their life. They wouldn't be able to book through the internet because they have never had a computer."
Last year, safety concerns forced Glastonbury organiser Michael Eavis to introduce a "super fence" to keep those without tickets out.
Mr Eavis said he knew nothing about the rave.
Security at Glastonbury was increased in 2002
"As far as I'm concerned it's a no-go area all around Glastonbury for the months of June and July," he said.
"The police will be quite alert to the possibility of something going on. We'll have roadblocks miles back.
"It's the usual season of rumours and threats."
Five Live reporter Phil Mackie said police would be overwhelmed if thousands of people suddenly descended on one location without warning.
Police are watching large areas of land in Somerset, Wiltshire, Devon, Cornwall and Dorset but would only be able to throw a cordon around the event, he said.
Last year, about 700 people who could not get into Glastonbury were forced out of the area by police and held an illegal rave at a disused airfield at Smeatharpe in east Devon.
We're well aware of the likely sites and we keep an eye on those sites
About 150 police surrounded the privately owned airfield to stop thousands of others getting in.
This year, police forces in the south west are working together to stop ravers gathering, a spokesman for Avon and Somerset police said.
"They are very flexible, but our approach is that we're well aware of the likely sites and we keep an eye on those sites and the likely people attending."
Local landowners had also been warned to be vigilant, he added.
Illegal raves became common in the late 1980s with the rise of the drug ecstasy.
But were largely stamped out by the 1994 Criminal Justice Act after an event at Castlemorton, Worcestershire, for 20,000 people two years earlier.
Chris Harris of Birmingham-based magazine Breaking Out told Five Live such parties were becoming popular again because clubbers wanted to get back to their roots.
"People just want to go out and listen to good music and don't really care how good the DJ is or how famous they are," he said.
"A lot of these things are getting very expensive."