Oxford Street at Christmastime is a special hell, and the last Monday in November is no exception. Grim-faced shoppers mummified in winter coats shove their way down freezing pavements to do their duty to the market, while a panopticon of corporate-sponsored festive lights glares down from slate skies. With no warning, a hundred young protesters pour across the road holding banners and whistles. The children of Britain are leading the consuming classes to mutiny.

These young activists are the same students and school pupils who were kettled in central London on 24 November after demonstrating to protect higher education. They have not gone away. They come from the buses and the Underground, pouring out of the backstreets in twos and threes, chanting: "No ifs, no buts, no education cuts!" The target is the flagship store of Topshop, the global byword for successful British commerce, owned by Philip Green, billionaire and business adviser to the Prime Minister.

When we were young, this world-famous, multilevel store, with its blaring music and cool-looking young employees, was an Aladdin's cave of consumer delights and cutting-edge fashion. Now, however, the sales tags have fallen from our eyes. "Philip Green's taxation could pay for our education!" the protesters chant, accessorising their woollies with clashing orange bandanas, two fingers stuck up at the matchy-matchy aesthetic of the Kate Moss display. "Please occupy Topshop for us," whispers a young shop assistant with exciting, angular hair. "We're right behind you."

Green revolution

This youth movement isn't just about university fees - it's about challenging a political class that systematically gives the needs of the market greater priority than the people, offering tax breaks for big businessmen while ripping the heart out of education and social security.

Britain's child crusaders are beginning to win the argument, the raw edge of their righteous indignation slicing through the semiotic debris of state propaganda. Messages of solidarity come from all sections of the public - from parents, teachers, social workers and even police officers. Teenagers who came to buy novelty tights and lip gloss toss their bags down and join the protest.

When the demonstration ends, we march back to the student occupation at University College London, a welcoming space where smiling people hand out cups of tea and draw up well-being committees. These kids are savagely organised. Watching them plan their next action, I feel that someone really ought to have warned David Cameron not to underestimate the bloody-mindedness of British youth. These young people are angry. They are angrier than anyone could have anticipated.

What has been taken from them to make them so angry? Hope, that's what. Hope, and the fragile bubble of social aspiration that sustained us through decades of mounting inequality; hope and the belief that if we worked hard and did as we were told and bought the right things, some of us at least would get the good jobs and safe places to live that we'd been promised.

Hope was the emotional engine of a decade of dizzying economic growth. Now it's gone. Thatcher and Reagan knew you couldn't take away hope altogther, which is why they replaced the politics of collective bargaining with a cynical, but seductive, politics of aspiration and individualism. The coalition has forgotten that it's not enough for millionaire politicians to preach the politics of austerity when all they have to offer is more austerity.

Back on Oxford Street, as the police vans scream into view, the children's crusade stands firm. "They want to marketise our education," says Ben, 21, his breath clouding in the bitter air. "So we're going to educate their market."