A series of arrests of cameramen and photographers has prevented images of demonstrators being arrested getting to newspapers and broadcasters this year. The National Union of Journalists (NUJ) believes that the practice is on the increase even though most cases are thrown out of court.
Last week a cameraman from the production company Undercurrent was arrested with a group of protesters who had occupied the offices of Rank Leisure to protest at the company's plans to build an Oasis holiday centre in the Lyminge Forest in Kent.
"First they tried to arrest me on suspicion of burglary," Roddy Mansfield said last week. "When I showed them my NUJ card they took it off me and asked me to quote my PIN number. Because I could only quote two of the numbers while being held by two burly officers they then arrested me on suspicion of forging the press card.
"The plan was to sell the footage of these hyped-up tactical support group officers coming through the windows to arrest these women protesters. But they seized my tape as evidence."
Undercurrent Productions, which makes programmes for Channel 4, has conducted its own survey of cameramen and journalists who cover protests and believes that 15 have been arrested this year in the course of doing their job.
Most notorious was the case of Nick Cobbing, the only photographer to get into the trees at the Manchester Airport protest site. The rest of the press was kept in a pen close to the site and could not get photographs.
Mr Cobbing got agreement from the climbers hired by the sheriff's department to stay in the trees and take photographs. When they asked him to come down with them he came down.
But once he was back on the ground he was arrested by the police for obstructing the sheriff's officers.
"They took my cameras and film and held me in a van at the site for two hours. Then they drove me to Salford police station where I was held for another 12 hours."
By the time he was bailed - on condition that he did not return to the site and that he stayed in his London home every night - no newspapers could use his pictures of the arrests and so none appeared.
A spokesman for the Metropolitan Police said that there was no policy to stop media coverage of protests. "But anyone who puts pen to paper or takes a photograph these days claims to be a journalist. It is up to the officer at the time to arrest whoever they think is breaking the law, it wouldn't matter whether they were a journalist or even an MP."
Tim Gopsill, of the NUJ, believes that the new kinds of protest, whether they be against new roads or treatment of veal calves, have brought new tactics from the police. "For a policeman to arrest a journalist while he is doing his job can only mean his intention is to stop the protest being reported," he said. "The increased arrests we are seeing could be attributable to the changed nature of protests we see. People aren't marching in the streets, they are trying to obstruct the things they oppose."
The NUJ has won sizeable compensation from the police for lost earnings by photographers who have been unable to sell their pictures because they have been arrested.