Rioting and violence from previous May Day demonstrations moulded the "rapid response" tactics used by Scotland Yard yesterday.

The Met has also adopted techniques developed to combat football hooligans and violent animal rights' protesters, as well as learning lessons from the military. Yesterday's operation was masterminded at the control centre, known as GT, on the second floor in Scotland Yard's headquarters in central London.

Reports and surveillance film is analysed by a team of 154 officers who send out reserves from the Met, City of London Police, and the British Transport Police to deal with any potential trouble spots.

There are banks of television screens ­ 110 in all ­ to help monitor about 2,000 cameras in central London, including those used to enforce the congestion zone. At the centre of the riot-control strategy are teams of police spotters armed with cameras who trail the various groups of demonstrators. At the first sign of trouble, commanders at GT call up reserve officers, some in protective clothing and riot shields, who can flood the area.

There were 3,000 officers on duty in the centre of London and an extra 1,000 on standby in surrounding boroughs who could come in to deal with any serious outbreak of disorder.

The use of advanced intelligence teams was first developed by the Met to tackle football hooligans and animal rights' extremists.

As the police have altered their strategies many of the protest groups have also switched tactics in an effort to outwit them. One of the problems for police this year was the lack of advanced warnings by the anti-capitalist organisers ­ in the past, they have provided detailed plans on their various websites and flyers.

Deputy Assistant Commissioner Andy Trotter, who is in charge of the police strategy, described yesterday how tactics have evolved since the first violent clashes with anarchists and anti-capitalists on May Day three years ago.

Stung by criticism that the police stood back in 2000 and allowed demonstrators to dig up the gardens in Westminster before trashing the Whitehall branch of McDonald's and defacing statues, including that of Winston Churchill, they now take a far more interventionist approach and deploy more officers.

The following year, police used the controversial system of penning-in hundreds of demonstrators as disorder broke out in Oxford Circus. This tactic, in which some people were corralled for up to eight hours, was criticised by some for being heavy-handed and punishing genuine demonstrators as well as the troublemakers.

"The unfortunate thing was as people were released they attacked us from behind and trashed shops and property," recalled Mr Trotter.

To prevent this reoccurring the police now forcibly push people away from the flashpoints and try to prevent them regrouping.

Last year, several hundred protesters broke away at the end of the main demonstrations and regrouped in the side streets of Soho where they clashed with police during the evening. Mr Trotter believes the lesson from that was not to leave a vacuum between the frontline officers and those in reserve. "It's not dissimilar to a military situation ­ if you move really fast you can leave a space behind you," he said.

He continued: "This year we have a lot of reservesfor all eventualities."