The Mayor of London, Mr Ken Livingstone, pledged yesterday to crack down hard on anarchists bent on violence in May Day anti-capitalist protests in the British capital.
Police promising "zero tolerance" towards rioters are staging one of the biggest security operations ever seen in London, with 5,000 officers out on the streets and all leave cancelled.
Protesters have vowed to target Oxford Street, the shopping heart of London, tomorrow.
The day could bring tumult to the capital because the protesters may also make a string of hoax bomb calls to provoke even more chaos.
Police are taking a much tougher line than last year, when they were accused of doing too little too late while vandals daubed the city's Cenotaph war memorial with graffiti and dug up the grass on Parliament Square.
The statue of wartime leader Winston Churchill has already been boarded up to ensure it is not attacked again.
Roundly condemning the motives of the protesters, Mr Livingstone said: "For them the objectives are scenes of mayhem like we saw last year when a lot of innocent people got caught up."
Asked by BBC Television what his message was to the ringleaders, Mr Livingstone said: "If you really believe in cancelling Third World debt and saving the environment then beating the hell out of a police officer or smashing in a shop window is really going to alienate public opinion. You will actually damage the causes you serve."
He warned that "at the slightest sign of violence, people will be arrested." There would be a lot of innocent people around tomorrow, the mayor said, and "if someone throws something through a plate glass window you can get those shards of glass that blind or kill".
"The complaints last year were more that the police didn't crack down harder. Last year I think we were all caught a bit by surprise by the scale of the violence that had been planned," Mr Livingstone said.
The mayor's remarks were echoed by the Home Secretary, Mr Jack Straw, who said he was confident the police could handle the situation. Mr Straw also recalled that he and Livingstone had joined street demonstrations in their youth.
"When we were taking part in a demonstration we were demonstrating for a cause," Mr Straw said. "One of the things we realised and we kept to absolutely was if you wanted to persuade people of your cause you didn't go into violence, which was wrong in any event," Mr Straw said.
"These people will be destroying their cause, just as they wreck property and cause injury and violence to police officers and civilians alike," he said.