Thousands of protesters were expected to congregate in London on Wednesday for a street party to mark what is dubbed as "Financial Fools' Day".

On the eve of the G20 summit, opponents of capitalism, environmentalists, and anti-war activists were to be joined by anarchists for "unprecedented" protests they hope would paralyze London.

Protesters were to march from four transportation stations toward the City, the hub of London's financial center, and set up camp outside the Bank of England to show their anger with "irresponsible", "reckless" bankers. Tons of sand were to be dumped in the center of the camp for children to launch a "sand protest".

Environmentalists also were to set a huge ice cube outside the summit venue in east London to show their concern about climate change.

In the meantime, anti-war campaigners were planning demonstrations outside the U. embassy following the arrival of President Barack Obama on Tuesday night.

Although organizers all claim the protests would be "peaceful", it was feared that anarchists were bent on creating violence.

"This (G20) is the biggest, most challenging and complicated police operation," Simon O'Brien, commander of the Metropolitan Police, said at a press briefing Monday.

O'Brien noted that the London G20 summit has attracted "significant and unprecedented protest" from different quarters. Some activists have re-emerged after years of silence. "They are galvanizing support for the protest in the hope of drawing 2,000 people."

Despite the challenges, O'Brien said British police are ready for the summit.

"We have the most experienced police officers in charge who are well-rehearsed in tactics," he said. "We're up to the operation and up for the operation."

In order to deal with thousands of protesters and the worst scenario similar to terrorist attacks on public transportation in 2005 when the G8 summit was held in Gleneagles, Scotland, officers from Scotland Yard, the London Police and London Transport Police have united under the Metropolitan Police, with extra support from neighboring Essex, Sussex and Bedfordshire police.