CARL COURT/AFP/Getty Images Police and protesters clash in the center of London on March 26, 2011 during a mass demonstration against government financial cuts.

Hundreds of thousands of peaceful demonstrators took to the streets this morning to protest government spending cuts. But by late afternoon a splinter group of rabble-rousers—dressed in black and wearing full-face balaclavas—had stolen all the attention.

The March for the Alternative—organized by Britain’s Trades Unions Congress (T.U.C.)—brought central London to a standstill as teachers, nurses, pensioners and assorted public sector workers marched from Victoria Embankment, along the western bank of the Thames, one mile west to Hyde Park. Some came dressed as monks, others as clowns; the former was a clever play on the country’s impending austerity, the latter on the perceived madness of government-backed measures. Some burned effigies of Nick Clegg and David Cameron, while others mocked them with comic book-inspired signage: “Bad Man and Robbing: Everyone is equal but some are more equal than others.” Regardless of the costume they wore or the banner they carried, all the protesters hoped to convey the same message: that the Coalition-led government—which has already tripled tuition fees for college students and announced plans to slash the police budget in England and Wales by 20%—is cutting too deep and too soon in its effort to reduce the deficit.

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“The government claims there is no alternative. But there is,” Brendan Barber, general secretary of Britain’s Trades Union Congress, told a gathering of thousands at Hyde Park. “Let’s keep people in work and get our economy growing. Let’s get tax revenues flowing and tackle the tax cheats. And let’s have a Robin Hood tax on the banks, so they pay us back for the mess they caused.”

For a breakaway group of protesters, pay back took the form of violence. Several hundred people—many of them from U.K. Uncut, a separate anti-cuts action group, others opportunists unaffiliated with any protest movement—descended on Oxford Street, London’s busiest shopping thoroughfare. By 2pm hooded activists were pelting police officers with light bulbs filled with ammonia, and by 3pm they were propelling paint bombs into the Niketown across the street. HSBC and Santander had their windows smashed, while paint and glass bottles were thrown at a nearby branch of the Royal Bank of Scotland. A violent mob attempted to storm Topshop’s flagship store, but only managed to break a window before riot police intervened. The haze of flares and smoke and shattered glass was just a prequel to the spectacle at 4:30pm. Several protesters wheeled a 20-ft. tall model of the Trojan Horse to the middle of the Oxford Circus roundabout and set it on fire. For a group that counts anti-capitalists among its lot, shutting down the city’s retail epicenter must have been a victory in itself.

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And while most of the protesters are driven by a desire to protect the public services they cherish, there are plenty who simply want to unleash a bit of anger at the upper-classes, who, they feel, should shoulder more of the burden, and at all those bankers they deem responsible for the financial crisis. Around 3pm masked youths launched trash cans at the windows of the swanky Ritz Hotel. And around 5pm around 200 protesters occupied Fortnum and Mason—the luxury retail shop known for its posh afternoon teas and hampers of champagne and Stilton. They broke windows, destroyed elaborate cake and flower displays, and held up a number of offensive signs. (One of the more G-rated ones read, “You can stick your royal wedding up your arse”). The BBC made its way into the store and caught much of the action on tape. Think Tet Offensive, but with tins of marmalade instead of guns.

Shoppers stuck inside the store never faced any real threats: a number of the demonstrators—most of whom looked like college students—could be seen laughing and having a jolly as they opened packs of expensive cookies. But the Telegraph found at least one man worried for his safety. “I came here to see my mother in a nursing home and we just wanted to find a nice place to eat,” he said. His wife, apparently speaking from a closet, described the situation as “terrifying.”

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Barber, the general secretary of the T.U.C., wishes the rogue elements of the march hadn’t caused such a stir—and hopes their behavior doesn’t muddle the message from today’s demonstrations. “These things are nothing to do with the T.U.C., and I regret very much that the actions of a few hundred people risk taking away from the attention of the hundreds of thousands of people who have taken part peacefully in the protest we have organized,” he said on national television this afternoon. “We’ve had hundreds and thousands of people come together peacefully to make a political point. The temperature is dropping [outside] but the temperature is rising for the government.”

Given today’s events, Mr. Cameron would be wise to keep an eye on the forecast.

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