Police will analyse hours of videotape to identify May Day riot ringleaders

Scotland Yard yesterday began a trawl through thousands of hours of video tape to identify a further 200 violent demonstrators and their leaders involved in the May Day riots in central London.

Police camera crews and photographers, many hidden, filmed the protest. In addition, dozens of surveillance cameras will be examined. An operation has been set up to analyse the film and photos, identify suspects and make arrests. Nearly 100 people have been arrested in connection with the disorder and the first offenders appeared in court yesterday. Police believe another 200 people were involved in criminal actions.

Photos of suspects will be posted on the internet, printed on posters and published in newspapers in the hope members of the public will recognise them. Police will pay special attention to demonstrators filmed with flags and mobile telephones, who detectives believe were orchestrating some of the violence. Deputy Assistant Commissioner Michael Todd said: "The disorder was obviously highly organised by a small number of people who were co-ordinating events ... identifying, arresting and bringing to justice those responsible has already started. We will do everything we can to ensure that these people are found."

Analysis of surveillance material follows a similar operation after rioting in the City of London and at Euston station last year. A lesson learnt then was the importance of obtaining photographic evidence. A failed attempt by police to force media to hand over pictures and film has resulted in the greater deployment of police camera crews. Demonstrators rounded up on Monday were checked against photos of suspects still wanted from the previous rioting in London. Veterans of violent protests use a variety of hats and changes of clothes to disguise themselves.

Yesterday Scotland Yard said officers stood back while demonstrators committed low- level vandalism on May Day, for fear of provoking violence. But law-breakers would be prosecuted, the spokesman said.

Activists from Reclaim the Streets, one of the protest organisers, distanced themselves from the violence and said of the defacing of the Cenotaph: "We do not necessarily celebrate the generals and the ruling class that send people to their deaths in order to protect the privileges and control of the few. The abhorrence of sending millions of men to their deaths in the trenches dwarfs the stupidity of any possible slogan on any possible piece of stone."

Those who appeared in court yesterday in connection with the rioting included a British Telecom telephonist, Richard Stephens, 28, of Bristol, who was jailed for 14 days after admitting using threatening words or behaviour.

Alan McAlve, 38, from Rochester, Kent, was jailed for 90 days for using threatening words or behaviour. Jan Erlstedt, 31, a designer from Slough, Berkshire, who admitted obstructing the highway in the Strand, was fined £100.