A peaceful protest. The inevitable aftermath

Up to 500,000 people marched in London yesterday against the Government's cuts. Should we allow the violence of a tiny minority to detract from Britain's biggest demonstration in eight years?

There were two demonstrations in London yesterday. The first, and most enduringly important, was that by half a million people against the cuts that are falling disproportionately on vital public services and those who provide them.

The other one was a demonstration of just how easy it is for a few hundred people to steal the occasion with sporadic acts of violence. Last night, it the latter one which was taking the headlines as police and protesters clashed in Trafalgar Square.

Earlier half a million people descended on central London for the biggest protest the nation has seen since demonstrations against the Iraq war eight years ago. They streamed into the capital from across the country to vent their anger at government cuts, their only weapons peaceful chanting and waving placards. There were 500,000 people and, with their disperate causes, represented 500,000 different reasons to take a stand.

From students facing rises in fees to parents whose Sure Start services are being slashed, the message was the same: "Stop the cuts." The March for the Alternative was organised by trades unions, but its anti-cuts message chimed with a much wider audience. Hundreds of coaches were chartered and public transport full to bursting as people came from across the country. Diane Richards, 62, a nurse from Aberystwyth, was one. She said: "I was born in the same year as the NHS and I'm doing better than it. Politicians have no concept of the impact of these cuts on small communities, poor communities."

The turnout was so high that it took more than four hours for the last marchers to leave the starting point on the Embankment. The banks of the Thames became a sea of colour as the road was filled with banners, balloons and entertainers. Many of those snaking through the city, past the Houses of Parliament and towards a rally in Hyde Park, had their children and babies with them.

But other protestors - a few hundred at most - brought with them splintering glass, flying paint, smoke, and violence. As night fell, a hardcore of protestors continued skirmishing with police in Trafalgar Square, and a blaze started deliberately in Jermyn Street had to be extinguished by firefighters.

The trouble had begun in the afternoon as breakaway groups targeted London's main shopping streets. At Leicester Square, Piccadilly Circus, Mayfair and Oxford Street anarchists hurled smoke bombs, glass bottles and lightbulbs filled with ammonia. Late into the evening, an apparent attempt by protesters at camping in Trafalgar Square to turn it into a British version of Tahrir Square, the scene of the Egyptian uprising, descended into the day's worst skirmish with police. A party atmosphere with music and dancing turned into clashes with columns of police officers facing protesters throwing coins and bottles. Blood was lost from head wounds on both sides as police reinforcements tried to contain the crowds by using a kettling strategy.

This, and earlier violence in Oxford Street, at the Ritz and inside Fortnum & Mason, was a far cry from the peaceful passage along the Embankment in the middle of the day, when newcomers to demonstrating mixed with old hands. At the rally in Hyde Park the Labour leader, Ed Miliband, was booed when he told the crowd that some cuts needed to be made. But his speech was later applauded when he said: "Our struggle is to fight to preserve, protect and defend the best of the services we cherish because they represent the best of the country we love."

Brendan Barber, the general secretary of the TUC, told the rally that they were the real Big Society. He said: "We will fight the Government's brutal cuts in our workplaces and our communities. Today we are speaking for the people of Britain, and David Cameron, if you want to meet the Big Society, we're here in Hyde Park. It's time you started listening."

But it is the violence which was making the headlines. More then 150 people were arrested for public disorder and criminal damage offences following confrontations with police, who had laid on more than 4,500 officers. The police were using markedly different tactics from previous demonstrations, however, keeping in touch with the marchers via Twitter. The kettling that took place was mainly for shorter periods and away from the main protests.

The policing minister, Nick Herbert, said the main TUC rally had been a "testament to the British model of policing" but he condemned the violence in the West End as "completely unacceptable".

The luxury food shop Fortnum & Mason was one of the companies targeted in clashes. Protesters were kettled outside it by police as clashes became more frenzied. An anti-cuts direct action group, UK Uncut, had singled out the shop for a sit-in earlier in the afternoon, alleging it had dodged more than £40m in taxes. About 20 people occupied the roof while others scrawled the words "Tory scum" across its front.

Dressed all in black and with balaclavas and scarves covering their faces, groups calling themselves the Black Bloc rampaged across London's centre, smashing in the windows of bank branches, including HSBC, RBS, Lloyds TSB and Santander. The Ritz hotel, BHS, Topshop and a Porsche dealership were also targeted.

At HSBC, anarchist groups ripped up bins to smash the windows, throwing paint and "noise bombs" at the building and police officers. The group headed up Shaftesbury Avenue and sprayed slogans on a fleet of police vans and tried to smash their windows. Moving quickly to avoid being kettled by police, the group streamed towards Piccadilly Circus, scrawling the words "smash the banks" on walls as they went. Windows were broken at a branch of Ann Summers, a nearby McDonald's and a Starbucks branch as protesters chanted: "Whose streets? Our streets."

The Ritz hotel came under heavy pressure and was attacked by protesters carrying banners saying "globalise the resistance". They smashed windows and tried to occupy the lobby. Heading into Mayfair, the protesters – now numbering only about 100 – were involved in running skirmishes with police as they tried to attack buildings they believed housed hedge fund managers' offices. There were clashes when police formed a cordon in the protesters' midst, splitting them into two groups. Demonstrators wielding sticks charged at the single line of officers who responded by striking out with their batons. At least one, a female protester, was knocked to the ground by an officer, who then motioned to hit her again as she lay there, but appeared to pull away at the last second.

London Ambulance Service said 30 people were treated for injuries throughout the day, 11 of whom were taken to hospital, ranging from assault to collapsing with illness. Five police officers were injured. Four were treated for minor injuries and one was taken to hospital.

A spokesman for the civil liberties group Liberty said: "There can be no doubt that the official trade union-led demonstration was overwhelmingly civil, peaceful and good-natured and that the policing response was generally proportionate. However, the demonstration appeared to have been infiltrated by violent elements that periodically separated from the main route in order to attack before melting into the demonstration."

The Police: The Met tweets and texts in attempt to keep peace

When they were condemned for the "open air imprisonment" of kettling during the student demonstrations last autumn, some in the Metropolitan Police suggested the answer should be a more direct response, such as water cannon.

But yesterday's performance, often in the face of extreme provocation, showed the force had learnt much from those bruising encounters.

The charm offensive began on Tuesday, at a joint press conference with the TUC and the civil rights group Liberty. Assistant Commissioner Lynne Owens said that the force would be "naive" to ignore social networks. She added: "My message is that if anyone intends to cause violence, don't come."

The force's next significant message came at 10am yesterday: "For latest info re coaches parking at Battersea/ Vauxhall please go to..." It was the first of dozens of tweets and texts from the force, ranging from information on the progress of the march to public-service warnings about crime in the area. Officers had decided that new technology plus old-style engagement and communication with marchers was preferable to confrontation.

Finally, two Liberty lawyers observed Met control rooms – together with 100 legal monitors along the route – to ensure the force lived up to its promises.

Brian Brady

The Labour leader: Miliband's calculated risk backfires

When Ed Miliband agreed to speak at the "March for the Alternative", he took a calculated risk. It was organised by the TUC and so could reinforce the perception of him as the creature of the trade unions, whose activists secured his election as Labour leader. It was also likely to attract people bent on violence.

He avoided too close an identification with the unions because the march was broad-based enough to represent a wide cross-section of society. But he was caught in the second trap. Anarchists with black scarves hiding their faces timed their scuffles with police in Oxford Street to maximise Miliband's embarrassment. Moments after he started speaking, the BBC split the screen to show him side by side with images of running skirmishes outside TopShop. Sky News carried the sound of his speech over images of minor mayhem. In telling the demonstrators what they wanted to hear, he created another trap for himself. To compare a political disagreement over the pace of balancing the Government's books to the struggles of the suffragettes, civil rights movement and anti-apartheid campaigners was an analogy too far. And to quote Martin Luther King opened him to ridicule.

John Rentoul

Timeline

13:45 "Black bloc" anarchists break away from main march to charge up Regent Street.

13:55 Green flare triggers an attempt to storm Topman in Oxford Street.

14.10 Scotland Yard says ammonia-filled lightbulbs thrown at police.

14.30 Demonstrators attack HSBC bank at Cambridge Circus.

14.55 Ritz hotel in Mayfair becomes a target.

16.20 300 protesters occupy Fortnum & Mason in Piccadilly.

18.55 "Thunderflashes" - fireworks containing coins – thrown at police in Piccadilly Circus.

19.00 Large bonfire lit in Jermyn Street.

19.30 Base of Nelson's Column vandalised.

19.50 Many West End theatre shows cancelled.

20.15 About 40 protesters arrested outside Fortnum & Mason.