Battlefield

But the group, which included tunnel-digging environmental activist Swampy, failed in their attempts to prevent the sowing of the GM maize at Horselynch Farm near Littlemoor.

Dorset Police launched a major operation involving more than 35 officers and the force helicopter to ensure the planting went ahead safely.

Four arrests were made in what was an otherwise peaceful demonstration which lasted more than four hours.

The protestors said they would continue to live in the pink castle, a makeshift camp they erected last month at the entrance to the trial field ,to voice their anger at something which they claim is 'unpredictable, dangerous and unnecessary'.

They set up the camp on the first day that farmer Charles Foot was allowed to start planting the GM maize as part of the government's farm scale evaluations. Mr Foot, who is contracted to grow the crop on behalf of landowner Micky Jones, said he went ahead with the planting following advice from the government and bio-tech company Aventis, which supplies the seed and herbicide used in the trials.

Mr Foot praised the efforts of the police and said he found the protestors 'pleasant and polite'.

He said: "The job had to be done and there is no specific scientific or legal reason why it shouldn't have been done.

"The police acted swiftly and professionally. I thought it all came off rather well.

"I chatted to the protestors and discussed the issues surrounding GM crops.

"I found the people pleasant and polite."

Landowner Mr Jones and Aventis did not want to comment on the action.

Inspector Alan Jenkins who led the police operation said: "Our job was to make sure the farmer could go about his lawful business, to allow any lawful protest to take place and to ensure everyone's safety.

"We made four arrests in all, including one man for aggravated trespass, and we made a further three arrests after the people had unchained themselves from the tractors."

He added: "I thought it was a very successful operation. We achieved our objectives and fortunately no-one was injured."

The operation began at about 10am yesterday when several tractors and dozens of police officers descended on the field.

The tractors managed to enter the field although once inside two of them were blocked by protestors who chained themselves to the vehicles.

Mr Foot remained outside the field in a tractor which protestors climbed on top of.

Mr Foot said the police presence allowed the planting to go ahead on about two-thirds of the field.

The protestors, who include young families, organic farmers and students, hail from all over the west country. Yesterday's action included a contingent of hardcore protestors who have been involved in major environmental campaigns.

One of these was Swampy, the protestor who became a media celebrity in the 1990s following his unusual contribution to the protests against the Newbury bypass, the A30 link in Devon and the Manchester Airport extension.

He did not want to comment.

Pink castle resident David Cooper, 38, an organic farmer from North Dorset, said: "We saw a few policemen come charging in then lots of them emerged from the undergrowth.

"We were in a state of readiness for something like this to happen but the police seemed to come out of nowhere."

He added: "Since we've set up camp we've had a lot of support locally. People have been bringing us food and other presents. Our presence here is making people more aware of the GM issues.

"But this is not the end of it and we're not going to disappear overnight. We will have a group meeting and decide the next course of action. It may involve staying a couple of months."

Other people joining in the protest included concerned Weymouth and Portland residents.

Jan McCabe of Littlemoor said: "I was walking my dog by Teddy Bear Woods when all of a sudden some police officers jumped out of the bushes and told me I couldn't go any further down the path.

"I was shocked. I've never seen so many police in the Littlemoor area. The trouble is there's never a policeman around the estate when you really need one."

She added: "I never thought about GM crops before but I've learnt a lot about them since visiting the pink castle. I think their protest is very admirable."

Greenpeace member Ashley Reed, 34, of Portland, who is a regular visitor to the pink castle, said: "The action here against GM crops has generated a lot of support and people are becoming aware of the untold damage these crops can generate ecologically.

"Many see this form of protest as extreme and eccentric but these people are standing up for what they believe in.

"They are representing the views of what many local people feel. I think they are very brave."