The two-day showcase of Caribbean culture in west London attracts a million revellers to watch troupes of dancers in exotic costumes perform on floats as powerful sound systems pump out music. But this year's event is a huge test for the police in the wake of the riots, and they are flooding the area with 5,500 officers on Sunday and 6,000 on Monday, considerably more than last year. The festivities almost did not take place at all following the unrest, which was the worst in England for decades. The riots, which started in the north London district of Tottenham on August 6 before spreading across the capital and to other cities, caused enormous damage and left five people dead. Add to this the Notting Hill Carnival's reputation as a magnet for troublemakers, and many commentators thought it inevitable the event would be axed. Organisers were not ready to admit defeat in the face of an outbreak of civil disobedience, however, especially because the carnival itself originated as an act of defiant celebration in response to race riots in the 1950s. The carnival was founded in 1964 following the disturbances in Notting Hill six years earlier, which saw clashes between whites and newly arrived immigrants from the West Indies. "We are not going to let a minority stop us from doing what we want," Ancil Barclay, the festival's co-director, told AFP. "Cancelling the event would have had a negative impact and would have sent a bad message with the Olympics next year." London mayor Boris Johnson also urged people to "let the true spirit of London shine through", saying the carnival could help heal wounds left by the riots. Nevertheless, authorities are on edge. As well as the tight security around the festival itself, more than 4,000 extra officers are being deployed elsewhere in the capital in addition to the thousands who are normally on duty, police said. Police have also made at least 35 arrests ahead of the carnival and warned intelligence showed that gangs were planning to cause trouble. In addition, organisers have taken steps to ensure trouble does not flare up, with the festival starting and finishing earlier and extra stewards to keep order.