They hoped for 10,000, but in the end more than triple that number turned out on London’s streets for the biggest demonstration since the beginning of the economic crisis.

The Put People First march yesterday was organised by a collaboration of more than 100 trade unions, church groups and charities including Action Aid, Save the Children and Friends of the Earth. The theme was “jobs, justice and climate” and the message was aimed at the world leaders who will be gathering for the G20 summit here this week.

The marchers, estimated at 35,000 by police, accompanied by brass bands and drummers and a colourful assortment of banners and flags, walked the four miles from Embankment to Hyde Park, where speeches from comedian Mark Thomas and environmental campaigner Tony Juniper, and music from the Kooks, made for a party-like atmosphere.

People came from all over the country and families with children in push chairs were among those marching. Jyoti Fernandes, an organic farmer who travelled from Somerset with her four children, said: “We are here to remind people that we have to look after our land and look after our food.”

A group of fewer than 200 anarchists joined the march and were kept isolated and surrounded by police. Chants of “Burn the bankers!” were the closest anyone came to any show of aggression despite a heavy police presence and a few buildings along the route, including the Ritz Hotel, boarding up their windows. As protesters passed the gates of Downing Street, there were chants and shouts of “Enjoy the overtime”.

Thomas told the Observer he believed the protest marked “the start of a grassroots movement”. He added: “This is a moment. This is the first time people have had a chance to come out on to the streets in a big way.”

Kevin Stevens, 43, ignored police warnings for City workers to keep a low profile and came dressed in a pinstripe suit as a banker. “I thought I might prove all the talk about attacking City workers is nonsense,” he said.

Chris Knight, the anthropology professor suspended from the University of East London last week for suggesting that bankers might be lynched, was wandering the march alone. “I just met a copper and I said to him, ’Is this the revolution?’ He said: ’No, this is the dry run, the revolution starts on Wednesday. Midweek is when we will really start to dance’.”

Updates on the event and messages of support were quickly posted on social networking websites such as Twitter, which organisers encouraged people to use to provide live coverage. One blog dubbed the event as “Protest 2.0”.

Claire Melamed of ActionAid said the organisers were delighted with the turnout. “We’re really pleased. We are hearing every day about people losing jobs and not being able to feed their children as this economic crisis deepens. We want the G20 to listen to us - this began as a financial crisis and it’s turning into a humanitarian one.”

Police said there had been no arrests as of mid-afternoon, by which time the rain and wind began to disperse the crowds.

But Scotland Yard is expecting a greater challenge on Wednesday 1 April, dubbed “Financial Fools Day”, with a series of protests aiming to cause disruption in the Square Mile and elsewhere.