LONDON (AFP) - Hundreds of thousands of demonstrators marched in London Saturday in protest at the governments austerity measures, amid a heavy police presence that failed to stop outbreaks of violence. Huge crowds thronged the streets of the British capital holding banners and playing music in the demonstration against spending cuts introduced by the Conservative-Liberal Democrat coalition to tackle a record deficit. Trade unions said that up to 300,000 people took part in the March for the Alternative, with public sector workers, students and pensioners waving signs which read Dont Break Britain and No to Cuts. The huge turnout makes it the largest protest in the British capital since around one million people marched against the Iraq war in February 2003. While the main march was peaceful, the 4,500 police officers deployed to keep order could not stop outbreaks of violence in Londons main shopping district by a breakaway group of several hundred protesters. The black-clad, masked protesters got into scuffles with police, broke into a branch of bank HSBC and hurled missiles at Londons landmark Ritz Hotel. One was arrested on suspicion of being equipped to commit criminal damage, police said. But the violence was not on the same scale as that which hit huge student protests late last year against plans to triple tuition fees and it did not overshadow the main march, where there was a carnival atmosphere. Many families with children were among the protesters and the air was filled with the low-pitched bellow of the vuvuzela, the plastic trumpet whose droning provided the soundtrack for the football World Cup in South Africa. Bagpipers, steel bands, choirs and dancers were also out for the event. But, despite the festive atmosphere, there was much anger among the protesters. Gillian Siddons, a 60-year-old pensioner who had travelled from Scotland for the march, accused the government of creating a society where the rich get richer and the weakest get weaker. The government is making people pay for what the bankers did. They put us in a mess and we are paying for it, she said. After coming to power in May, the coalition announced cuts worth 81 billion ($131 billion, 92 billion euros) over five years in order to slash a record public deficit it blames on the previous Labour government. The march started by the river Thames, passed the Houses of Parliament and Prime Minister David Camerons Downing Street residence before ending in a rally in Hyde Park addressed by opposition Labour party leader Ed Miliband. Our struggle is to fight to preserve, protect and defend the best of the services we cherish because they represent the best of the country we love, Miliband told the rally. But speaking before the march, Education Minister Michael Gove insisted that the protests would not force a change in government strategy. The difficulty we have, as the government inheriting a terrible economic mess, is that we have to take steps to bring the public finances back into balance, he told BBC radio. A spokeswoman for the TUC, which organised the march and represents more than six million workers in many British trade unions, said between 250,000 to 300,000 people turned up. Police refused to give an estimate. The announced cuts involve most government departments, with the loss of 300,000 public service jobs and pay freezes for civil servants. Several student demonstrations descended into violence last year, with one culminating in protesters damaging the car carrying heir-to-the-throne Prince Charles and his wife Camilla.