It's just before midnight, in the damp chill of an austerity winter, and a gang of students and schoolkids is standing smoking against the iron railings outside an occupied lecture hall. "All that aspiration was pretty much for nothing when there are no jobs," says Amit, 18, a computer science student from Medway. "This fight is so much more important than blind careerism. Just don't tell my parents I said that."

It is the last day of November, and we are outside the Jeremy Bentham Room at University College London (UCL), the unofficial London headquarters of a national youth movement that has sprung up in protest at the government's cuts to higher education and welfare. Some of these protesters already have scars and bruises from the riot lines.

Behind the fire doors is a hub of light and activity. Amid the tangle of blankets and computer cables, students are sending out press releases, updating the group's Twitter feed and liaising with fellow dissidents about keeping the younger contingent safe on tomorrow's day of direct action against the tuition fees hike, which will involve tens of thousands of students and school pupils across the country.

“People have to stop talking about us like we're just idealistic kids," says a girl in a grey hoodie, jabbing her roll-up in my direction. "We're on the front line of a class war. We have a better understanding of this government's economic shock doctrine than most adults."

Then, behind her, another shout goes up. "It's snowing!" says one of the students, interrupting a debate on police brutality to rush over to the window. "It's snowing!" These members of the so-called lost generation press their faces against the glass, or hurry towards the doors to go outside and catch fat, frozen snowflakes on their tongues.

These young people have been radicalised extremely quickly. At the riots on 10 November, it was as if a pressure valve had been released as thousands of students and schoolchildren broke away from the sedate march through central London planned by the National Union of Students, occupying the Conservative Party's headquarters on Millbank, smashing windows and daubing slogans on the walls.

The anger and frustration that exploded at Millbank had been building quietly for years, as young people began to realise what a bleak future contemporary politics promises, and began to question if it has to be like this. "I got involved after Millbank, because that was when I realised we didn't just have to lie down and accept these cuts," says Jack, 30, a mature student from Gateshead. "When we bailed out the banks, young people realised that capitalism had screwed us all. But after Millbank, the possibility of resistance became real."

On the evening of 30 November, the realism that the girl in the grey hoodie observed kicks back hard. The latest protests organised by this diverse and decentralised network of young people run headlong into another round of beatings and arrests. Many students stumble back to UCL with bruises, bloodied heads and twisted arms after a breathless race through central London outflanking the police lines.

As the lost generation has begun to find itself, it has been met with brutal resistance from the authorities. "Yes, it's scary," says Tasha, a 16-year-old with a lisp and a tongue stud, "but it's wonderful, too. It feels like something real is finally happening, you know?"

Finally, something real is happening - that is the sense you get as a young person walking into this space, stuffed with sleeping bags and suitcases and scattered schoolbooks, plastered with slogans and messages of support from around the world.

Everyone remembers their first protest march, so that romance is nothing new. What is new is the means of resistance - the tools, from Twitter and Facebook to auto-updating maps of the riot lines - that have carried the energy of this movement into the new year and beyond. These young people are idealistic, but they are also pragmatic, and they have the technology to build networks and share ideas quickly. The fight they've signed up for requires all three.

They come from all over the country, from across the world, and from different backgrounds, defying every stereotype of the privileged, white, middle-class, male student radical. "I left school at 16 and worked in a carpet warehouse, and my political involvement was community volunteering - the 1980s recession never really ended in the north-east," says Jack.

“Until Millbank, I used to think that student politics was just a lot of liberal wankers, frankly. But this lot really care about workers - they care about ordinary people, they're liaising with unions and community organisers. It's not just about student fees. It's about fighting the cuts as a whole, and insisting that education, job security and welfare support are every person's right."

This is not business as usual for student politics. The polite institutional equivocation of the National Union of Students has been rejected. These activists prefer to hold more confrontational demonstrations - unplanned marches and attention-grabbing stunts that shut down big shopping centres and excite the global media. News of its impact is inspiring similar protests across Europe.

For most, politics used to be something that happened on television. Now, increasingly, it happens on the internet and everyone can be part of it. At UCL, the social networking machine is guided by two young men in their early twenties, and because both of them happen to be called Sam, they earn the monikers Techie Sam and Sam the Techie.

They spend most of their time huddled around a makeshift bank of ­computers together with a stream of helpers, coding, blogging and making sure that the various occupations and sit-ins across the country stay in touch.

The internet was supposed to make our generation apathetic and disconnected, but it has become a tool to turn back on the authorities, allowing us to make links and mobilise farther and faster than any previous cohort of radicals could have imagined, outstripping the sluggish machinations of mainstream political parties.

Techie Sam wasn't political two weeks earlier. A shy, stocky young man who looks older than 22 and professes libertarian tendencies, he got involved after his girlfriend, Jenny, was caught in the front line as police launched a horse-charge against student protesters outside 10 Downing Street on 24 November.

After Jenny was trampled and traumatised, Techie Sam realised that "peaceful protest was no longer an option. I feared for my safety if I dared to go on the streets, so I decided to offer my particular skill set to the movement and to help in the way I know how."

He now finds himself working so many hours a day that he's taken to sleeping in a roll of blankets under his desk in the room at UCL. It's not just Techie Sam. All of these young people are working hard, teaching one another about the best ways to resist police strong-arm tactics, putting their message out to the press and spreading the word: this is a resistance movement, and you can join in.

After a brutal police kettle in Whitehall on 24 November, in which thousands of children were penned like cattle in sub-zero temperatures, without food, water or shelter, for daring to speak up against the government's austerity programme, Greek students held a rally outside the British embassy in Athens to express fellow-feeling. They were tear-gassed for their trouble, and many were hospitalised.

Back in London, students watched the live feed in horror. Three days later, they led their own rally to the Greek embassy. A young art student from Athens - 22-year-old Margarita, dressed in denim, and a whizz with video installations - was persuaded to lead the British protesters in a chant of solidarity. She shouted a line in Greek and the Brits - the loudest of them a squatter with a thick Glasgow accent - chanted it back as best they could.

On the long journey home, Margarita was asked precisely what they'd been shouting. "Oh, it's just something we say in Athens when the police beat us," she said, smiling.

“It translates something like, 'Cops, cops, you're all murderers, we hope you die.'" Members of the "media relations working group" turned pale.

“I object to politicians using the term parliamentary democracy, because I don't think we have one any more," says Ben Beach, 21, an architecture student who has been awake for 28 hours when we first meet.

“No one has the balls to stand up and represent the people they're meant to represent. We're about to be made to pay for a financial crisis that we had no part in creating. Education and welfare are being destroyed to pay for a £1.4trn bank bailout that wasn't our fault."

Ben Beach is the Justin Bieber of the new left: a baby-faced riot messiah from Bethnal Green in east London with a tendency to hog the megaphone at demonstrations. He was trained in street activism by the Socialist Workers' Party, making him one of a minority of student protesters with a background in far-left politics. It was Ben who, when the Labour MP Jon Cruddas visited the UCL occupiers, pulled him up for speaking to the students as if they were not his ideological equals.

“Don't patronise us," Beach told him. "We're using an economic model that's based on debt - and that's why every decade we have a recession, each one worse than the last, and why every time the poor are hit hardest. The root of this crisis was the free market, and the only solution we've been given by any political party is more of a free market. Parliament is not addressing what caused the problems, and so society needs to."

A similar view comes from Aaron Peters, 26, a former member of David Miliband's Labour leadership campaign team with a tendency to pull an Incredible Hulk act when out on protests. "Parliamentary politics is basically over - it's dead," he says.

On 3 December, as workers and students occupy and shut down Topshop's flagship store in central London to publicise corporate tax avoidance (see Samira Shackle, page 29), Peters is quietly informed that he is, in fact, wearing a T-shirt from Topman. He immediately rips it off and stands shirtless on Oxford Street, stating that, even in sub-zero temperatures, one does not need exploitatively made clothes if one has the right ideals.

Peters and Beach are the sort of leader that this staunchly leaderless movement would otherwise have. Instead, the UCL occupation, and the movement as a whole, pursues a policy of consensus-based decision-making, an anarchist organising structure that gained credibility with the rise of green protest. Under this system, which involves hand gestures and autonomous working groups, there is no central leadership to report to. This means that everyone is allowed the chance to speak, and that the voices of women and younger pupils are given priority. It also means that direct action can be effected quickly, without any need for the bitter, arthritic infighting that blighted the student protests of the 1960s and, more recently, the Stop the War movement. "They said it couldn't happen; they said that students could never mobilise like this," says Peters who, thankfully, was fully dressed for the visit to UCL by Cruddas. "Well, now we're everywhere. This is just the beginning."

Clothes are a perennial problem. When Peters and Beach - who, like the rest of the gang, are quite prepared to get arrested if need be - stage a two-man protest outside a speech on education and the economy given by Gordon Brown at Bloomberg's London headquarters on 8 December, they need smart jackets to get into the event.

This is difficult because, after two weeks without hot showers, clean clothes or enough sleep, the members of the occupation have all drifted into a collective vagrant aesthetic. Eventually a three-piece suit is procured by way of a young man whom I'll call "Peregrine", a barman and student at a local college who also happens - he reveals shyly in the third week - to be an aristocrat, which is why he is always asking everyone for money. Outside the Brown event, Beach gets a phone call from Peregrine. "Um, Ben, you may want to check out that waistcoat before you go past security, OK?" Peregrine says. "I think there's some, like, acid in the lining."

As I watch Beach frisking himself, as if his clothes were full of itching powder, a strange thought occurs. In a world where bankers can hold governments to ransom and where Tory ministers worship the free market with a cultish obeisance, these young nutcases may, in fact, be the sane ones.

Tellingly, the UCL protesters, unlike the 1968 generation with which they are so often compared, are - on the whole - drug-free, and have banned drinking at meetings and sex in the toilets. They don't want to ruin their reputation with a media machine that is already villainising some of their members. Besides, there is no time: they are too busy building links with trade unions, geeing up local councils and hounding Tory ministers outside public events, and some of them still have essays to write. These young people have been raised to work hard and play hard, and now they are turning that dedicated single-mindedness into a weapon.

Besides the merciful lack of dominance by a far-left-party vanguard, this is something else that differentiates these activists from the 1968 generation, and from those who fought Margaret Thatcher's reforms in the 1980s: they are in no way hedonistic or self-indulgent.

What shocks even more than the straight-edged sexual abstinence of the protesters, however, is the way this new politics affects how these young people relate to the world and to one another, working together, facing down the police together, sleeping huddled for warmth on cold floors.

On the morning of 9 December, the day of the Commons vote to triple university tuition fees, the protesters fumble out of their sleeping bags, pull on boots and woollens and prepare for battle with the police. It's going to be the biggest demonstration yet.

“People died at the Brixton riots in 1981," Ben mutters. "People might die today. We all know what's at stake." There is a resolved silence as they pad their jackets with protective cardboard and scribble lawyers' numbers on their arms.

Peters calls for silence as Techie Sam puts a YouTube clip on the projector. A well-known actor's voice floods the hall, reciting from Henry V: "We few, we happy few, we band of brothers;/For he to-day that sheds his blood with me/Shall be my brother . . ." Ten hours later, many of these same teenagers will stagger back from the protest with blood running down their faces.

“Whatever happens now, everything has changed," 23-year-old Sarah writes in her blog of the occupation. "We've changed. Politics is the main topic of conversation. Demanding our rights has became normal."

In the occupied college building, education is not a commodity, but an intimate weapon of social change, and Sarah seems to understand that better than anyone else. She grew up on a working farm in South Wales; she wears sensible fleeces and non-designer spectacles.

Only gradually, after spending time with the occupiers, do you realise that it is this soft-spoken geography student, not the more dramatic male activists, who is running the show, organising the meetings, making sure the younger ones are listened to. "This is like a family," is how Sarah puts it on the blog. "That's the beauty of it. It's the sense that anyone can speak and be listened to; like any of these people I didn't know last week would come to my rescue if I needed it."

That night, on 9 December, in front of a line of mounted police, as tens of thousands of protesters surge past the barriers into Parliament Square, I find myself standing next to Sarah, watching her throw up her hands to protect herself and others from a hail of batons.

Sarah's sensible fleece is flecked with blood, but she stands firm until the police run their horses into the crowd, pushing the protesters into a pen with nowhere to run. We stand until we are forced to the ground, crushed under a writhing, kicking heap of bodies. I grab Sarah's arm and we go down together.

Friendships always form quickly on the barricades, but this time a sense of solidarity is more important than ever. What is at stake here is not just the future of education in Britain - the catalyst for the protests - but a complete reconfiguration of the way young people understand civic society and their place within it.

Being born at the end of the 1980s was like rocking up in the small hours of a wild, destructive party and being asked to help with the clean-up, sweeping the fag ends off the floor and washing the stains off the sheets. We'd hardly arrived before Francis Fukuyama declared "the end of history" and the final victory of liberal capitalism. This year, it's all changing. This year, That­cher's children, the generation that was sold out and sold down from the moment we learned language, took a stand against the glacial creep of corporate oligarchy. In 2011, the eyes of the world are on Britain.

As the protesters hobbled back in from the kettle and headed home for the Christmas holidays, they promised to keep the energy going. By late January they were living in each other's houses, going to planning meetings every day, building links with trade unionists and workers' organisations that feel - in the words of Unite's Len McCluskey - "put on the spot" by the student protests, which "refreshed the political parts a hundred debates, conferences and resolutions could not reach".

“This started as a protest; now it's a full-scale resistance movement against the cuts," says Ben Beach. "The difference is that protesting is just people objecting to something. Resistance is people saying, 'We will not let this happen.'"

Frantz Fanon wrote that every generation must "discover its mission, and fulfil it or betray it in relative opacity". There is always the possibility that this generation could betray its mission; that the energy of resistance in this new movement could dissipate, dissolve into infighting, or be sold into quiet complicity. The leaderless, dispersed system of organisation, however, outstrips the traditional sectarianism of the old left, and selling out seems particularly unlikely: these young people, as they are constantly reminded, have precious little to sell.

Unlike the student uprisings of 1968 and the anti-globalisation movement of the late 1990s, there is no surplus of energy and jobs, and no easy careers left for these young people to escape into. Most of those who aren't already unemployed and outraged have no idea what they'll do when they leave school or college, apart from carry on fighting.

On 9 December, just before the tuition fees vote was lost, I saw a young woman standing in the crowd in the Westminster kettle, holding a sign that read, simply: "Where's all this going to end?" The truth is that not one of us knows: this is an emergent movement, and with the stakes so high, the endgame is still obscured.

One thing's for sure, though: it goes far beyond a parliamentary battle over the Education Maintenance Allowance and student fees - the loss of those votes has, if anything, strengthened the resolve of the student protesters. Their struggle is about free education, but it is also about freedom itself.

This movement is redefining how politics is done in this country and across Europe. It is the pursuit of a politics that is not passive, but intimate and interactive. The mission is also persistence, but that won't be a problem. I am writing these last lines in a hall packed with new members of the movement, readying themselves for resistance days between now and March. "We lost the vote," says Jack. "But we've still got everything to fight for."

Web editor's note: An earlier version of this article wrongly attributed Sarah's quotes, which come from her blog of the occupation. This has now been updated. The quotes were used with Sarah's permission.

Some names have been changed.