Police today entered an environmental protest camp near Heathrow to carry out an inspection of the site after the landowner complained that the land was being illegally occupied.

Chief Superintendent Ian Thomas met camp organisers as other officers toured the settlement and talked to campaigners, who emerged from tents, blowing whistles and shouting “police on site”.

Police have sealed off Sipson Lane, between the villages of Sipson and Harlington, where the field is located.

The week-long demonstration to protest against the expansion of Heathrow had been due to start tomorrow, but police estimated that 250 protesters had already arrived by this morning, pitching a number of tents and marquees with banners at the camp entrance reading “Climate Camp - no Airport Expansion” and “Runways to Ruin”.

Organisers expect more than 1,500 people from across the UK and other parts of Europe to join the event, spurred on by BAA's high profile legal action against the campaigners.

BAA, the Heathrow airport operator, tried to have a wide-ranging banning order imposed, claiming that some protesters might attempt to disrupt flights, but had to content itself with a limited High Court injunction forbidding direct action that could interfere with air travel..

Chief Superintendent Thomas said that 25 officers inspected the site this morning at the landowner’s request. He said the protesters were on the site illegally, adding that police had repeatedly asked to send in a small team of officers to check that there had been no damage to the site or any offences.

Police had made two arrests, before this morning’s visit, one for suspected deception and another for an outstanding criminal warrant.

Mr Thomas said: “It’s very peaceful so far but the main problem is that they have set up on land where the landowner doesn’t want them.”

Camp organisers have now agreed to allow four officers to remain on the site.

Sophie Stephens, a member of the camp’s media team, said police arrived on site unannounced and appeared to be “flexing their muscles”. No one had been arrested or evicted during the visit and there had been no trouble, she added.

Organisers said the first few days will be taken up with 100 workshops on green campaigning skills and methods of direct action, culminating in a day of action next Sunday.

Gary Dwyer, 34, a protester from Headingley, Leeds, said: “This is a forum of different individuals who want to take action against the root cause of the climate change, to empower each other, to alter our lives and make the social changes that we know are necessary.

“Government and corporations are not going to make it better, in fact they’re going to make things worse.”

He said he expected the event to be peaceful. “There will be the day of direct action, but we’ve said there will be no attempt to storm runways or anything like that. Public safety is paramount.

“But there will be action, the BAA headquarters is only over there, and there are many carbon criminals to think about who are driving climate change.”

Up to 1,800 police officers from four forces will be on duty over the next nine days, amid fears in Scotland Yard that the protest will attract troublemakers. A similar camp last year close to the Drax power station in Yorkshire by 400 protesters led to 40 arrests.

Some civil rights activists have voiced concerns at police tactics, after officers made it clear they would deal “robustly” with any problems.

A camp spokeswoman, Alex Harvey, complained that police had refused to allow the site to connect with the mains water supply and had prevented food, plumbing equipment and other essential supplies to be driven into the camp. Medical equipment had been carried in by a human chain.

Ms Harvey also claimed police were stopping and searching people under terrorism legislation. “It is absolutely diabolical to be using terrorism powers in this way. We are not terrorists. It is a complete abuse of these laws,” she said.

Explore UK News

• Crime News

• Education News

• Health News

• Scotland News

Times Recommends

• Fern Britton: 'I still can't see that I was wrong'
• Extreme cooking
• Easy French: Tarte Tatin