The clashes came when demonstrators tried to storm the gates of Downing Street during a march against the Criminal Justice and Public Order Bill.
More than 35,000 people from a wide spectrum of groups including environmentalists, ramblers and ravers tramped through central London during a largely peaceful demonstration.
Environmentalists oppose the Bill because some clauses will effectively ensure that virtually any form of protest on private land will be a criminal offence. Ramblers oppose it because it significantly curtails their ability to walk in the countryside where no footpath exists. And civil rights groups are against the Bill because they regard it as attacking minority groups such as gypsies, travellers and rave partygoers.
The trouble started when protesters reached Whitehall. At 3.45pm a group of several hundred people stopped at the entrance to Downing Street and hurled bottles, cans and abuse at the police. Ignoring the pleas of the stewards for non-violent protest a mob of about 50 people tried to storm through the gates to Downing Street. Seventy police in full riot- gear including a dozen on horseback, drove a wedge through the protesters and forced them back.
Stewards, organised by Advance Party, an umbrella organisation representing ravers and party-goers, tried to keep the march moving and place themselves between the protesters and police. The police returned to Downing Street and Richmond Terrace opposite only to charge the protesters again five minutes later. Once again the stewards pleaded with the police and the violent element of the demonstrators to stop fighting. However, after 15 minutes violence flared again as a group of marchers again tried to storm Downing Street and were forced back by riot police. After a brief stand-off the protesters carried on to Trafalgar Square. Police closed Trafalgar Square for about three hours to allow the protesters to disperse peacefully.
The police said: 'We have in excess of 20,000 demonstrators. The vast majority of which were peaceful and well-intentioned. There were a few who decided to cause trouble and we had mounted police to deal with that situation.'
Six sound systems accompanied the march which resembled a carnival. Men on stilts handed out leaflets preaching non-violence. Advance Party and the Socialist Workers Party organised the march.