A man in a suit with a mobile phone who called the shots in the City riot

IN A SMART dark suit, with a brief case and a copy of the Financial Times under his arm, he looked like your typical City gent. Only after he dropped his props and began helping to unload a truck full of concrete blocks and wooden stakes did his allegiance become clear.

The man in the suit and the hire truck were part of what police believe to be a sophisticated and well-planned attack that brought some of the worst violence and public disorder to the streets of Britain since the poll-tax riots of 1990.

In five hours on the afternoon of 18 June, groups of demonstrators on an anti-capitalism protest in the financial sector of London ran amok, attacking police and causing pounds 1.2m of damage as they vandalised buildings and blocked off roads.

Since the rioting in the financial heart of Britain, a team of 60 detectives from the City of London and Metropolitan forces has been compiling evidence against the violent demonstrators. A key part of Operation Enterprise is being run from a video suite in the Bishopsgate police station, where five officers are painstakingly sifting through 5,000 hours of film from hidden police cameras, a helicopter and fixed CCTV monitors installed throughout the City.

The walls of the suite are plastered with photographs of police "targets" - alleged rioters caught on camera. They are brandishing scaffold poles, bricks, staves, a spade, or helping to unload a lorry full concrete blocks. Each suspect is given a number written next to the face, and cross-referenced to video sequences.

One section shows a police woman on a grey horse being dragged to the ground by protesters. The crowd tears off her helmet and repeatedly punches her in the head and body. One rioter is filmed reaching up to her saddle and stealing a side-handled baton.

In another episode, a camera captures a man with a shovel hidden by his side slowly approaching a line of police officers who were being confronted by demonstrators. The man quickly raises the weapon above his head and strikes an officer on the helmet, sending him tumbling.

In a third sequence, a camera on a police helicopter films protesters throwing bricks and rocks at officers then using two huge rectangular dustbins on wheels as battering rams.

So far, the police have photographs of 147 different "targets" said to be committing serious criminal offences. The police have names for 20 of them and have sent out folders of photographs to all Britain's police forces and Special Branches, asking them whether they can identify any of the suspects.

Detective Chief Inspector Kieron Sharp, of the City of London police, who is heading Operation Enterprise, believes evidence from the film and information from police intelligence shows the protest and violence were carefully planned.

Demonstrators were filmed arriving for the Carnival Against Global Capitalism protest at Liverpool Street railway station, where they were given four different coloured masks with legal advice written inside and information telling the protesters to follow organisers with matching coloured flags.

Two cars bought by organisers were used to block a road by letting down the tyres and throwing the keys away. A ring- leader dressed in a suit is filmed standing in front of the vehicles, signalling protesters to join him. In another video, a lorry loaded with ladders, staves and concrete blocks is brought into the crowd and unloaded near the London International Financial Futures Exchange (Liffe) building, site of some of the worst fighting.

Throughout the disorder, several activists are seen in suits as an apparent disguise. In one of the most blatant cases, a man puts down his briefcase and Financial Times to help demonstrators to unload a lorry. A man wearing a pale jacket is also filmed, apparently orchestrating the pelting of police officers with missiles. Several groups organised the protests, including the high-profile Reclaim the Streets.

Det Ch Insp Sharp said: "It's unbelievable how some police were not killed. There was very severe and savage violence. We knew there was going to be trouble, but we had no idea where it was going to be and we had no idea that it would be so well organised and so violent."

An independent report into the police handling of the riots criticised the City of London force for indecisive action, poor judgement and inadequate communication.

Det Ch Insp Sharp said there had been claims and rumours about further anti-capitalist mass demonstrations on 30 November and 4 January, the first working day of the next century. But intelligence suggested the demonstrators were unlikely to be able to organise another large event so soon.