The siege of Oxford Circus in London ended last night as police successfully dispersed the thousands of demonstrators they had contained for almost eight hours.
But the May Day anti-capitalist protests saw further violence as a hard core of departing demonstrators went on the rampage in the nearby and unguarded Tottenham Court Road area.
The Bank of Scotland, Abbey National, Barclays Bank, Coffee Republic and Habitat were among 20 business premises targeted. Rioters also attempted to set fire to a Tesco store in nearby Goodge Street.
Police confirmed that a group of 50 or 60 demonstrators had broken away and re-grouped as the controlled dispersal of thousands of demonstrators got under way after an eight-hour standoff.
The number of arrests rose to more than 50 - with many arising from the possession of lock-knives, screwdrivers and other weapons - after a day of sporadic violence which saw at least 30 people taken to hospital, largely for treatment of minor injuries.
Scotland Yard confirmed that among those arrested were eight people from Denmark, Poland, Belgium and the US.
One man suffered head injuries when he was hit by flying debris from the John Lewis department store.
He and two others with head injuries were being treated at University College Hospital.
A number of police officers sustained injuries in vicious close-quarter confrontations during the Oxford Circus siege.
At one stage during the early evening police were attacked with petrol bombs.
But the day was hailed a victory for a long-planned and carefully executed police plan which relied on the overwhelming force of numbers, the ability to trap protesters and isolate trouble-makers, and the much-vaunted "zero tolerance" of any violence.
The Home Secretary, Mr Jack Straw, congratulated the Metropolitan Police for "a very, very professional operation".
He denied that advance warnings of anarchist-inspired mayhem had been exaggerated, and said the relatively minor levels of violence experienced were the result of police planning.
The Mayor of London, Mr Ken Livingstone, praised the police action as "an example of policing at its best".
However the anti-capitalist demonstrators were also claiming success last night after a daylong street action estimated to have cost London business in the region of £20 million through lost trade, damage to property, and additional security costs.
Despite defiant "business as usual" declarations in advance of yesterday's demonstrations, many shops and businesses from Oxford Street to the City were closed.
Train, tube and bus services in and around central London were severely disrupted.
Policing costs alone - there were 6,000 officers on the ground with another 3,000 on standby - were put at £1 million. And Westminster Council's director of leisure and environment, Mr Joe Duck worth, said "the entire city of Westminster will feel the ramifications of these protests".
Earlier protests, described as "more Rio than riot", had involved the distribution of veggie burgers outside a MacDonalds, the construction of a cardboard hotel in Mayfair to highlight the plight of the homeless, and a slow cycle ride by hundreds of anti-car protesters which blocked Euston Road, one of London's main arteries.