As the global economic downturn gathers pace, police in the UK say protesters are planning in an "unprecedented" way for London's G20 summit next week. But who are those taking to the streets and what do they want?
The coming together of the world's biggest economic powers has always attracted vocal and sometimes violent demonstrations.
But this year there are fears that anger over the recession could make next week's G20 meeting of the world's most powerful countries the focus for mass protest on a scale not seen for some time.
The Metropolitan Police warned last week that anarchists and environmentalists were planning in an "unprecedented" way ahead of the summit, and that groups active in the late 1990s were re-emerging and forming new alliances.
And Foreign Office Minister Lord Malloch-Brown has said anger over the financial crisis will mean people are more likely to "sympathise" with the hard-line G20 protesters.
Those inside the more radical groups themselves have claimed a "groundswell" in support, and warn the downturn is bound to boost numbers on the streets before and during the summit on 2 April.
A number of coalitions - both mainstream and militant - have formed to co-ordinate action ahead of G20. They will be campaigning on a vast range of subjects, from poverty, inequality and jobs to war, climate change and capitalism.
So, who will be waving what banners next week?
In the first scheduled protest on Saturday, thousands are expected to join the Put People First march through London, when more than 100 charities and unions will call for democratic governance of the world economy, measures to tackle climate change and an end to global poverty and inequality.
The alliance brings together household names, such as development charities ActionAid, Oxfam and Plan, green campaigners Greenpeace, Friends of the Earth and Stop Climate Chaos, and jobs and homelessness groups like the TUC, the Salvation Army and Shelter.
Organisers of the march - which police say is not expected to be "anything other than lawful" - argue that protesting this year is particularly important because the downturn is hitting the poorest hard and is offering governments an opportunity for change not seen for decades.
"Many people think things are possible now who didn't think so six months ago," says Dr Claire Melamed, head of policy at ActionAid. "And that's not just among NGOs [non-governmental organisations] but also in the government."
Plan's UK chief executive, Marie Staunton, agrees that London's G20 comes at a "pivotal time" and says it is crucial that richer countries take advantage of the recession to make changes to tackle poverty and climate change.
"There are some very simple things that could be done if there is the political will to do them," she says.
In addition, veteran campaigners CND have joined forces with Stop the War Coalition, the Palestine Solidarity Campaign and the British Muslim Initiative.
They will stage a demonstration on 1 April calling for the abolishment of nuclear weapons and the removal of foreign troops from Iraq and Afghanistan, as well as action over the Middle East.
But those groups of most concern to the authorities are the band of activists planning direct action, including Camp for Climate Change Action and those acting under the umbrella name G20 Meltdown.
Climate Camp - the group behind direct action at Heathrow Airport and power stations in North Yorkshire and Kent - has been using text messages, e-mails and social networking sites to plan what it calls a day of "spectacular action", which will see supporters "set up camp" in the City.
It has seen support grow, with more than 1,000 people already signed up to the group's Facebook site ahead of the 1 April protest against the policy of carbon trading.
"I don't think that there has been such a clear sense of the need for change in the general public for quite some time," said one Climate Camp member.
"That's bound to reflect in greater levels of unrest on the streets."
Meanwhile, G20 Meltdown is appealing to those who have lost their "homes, jobs, savings or pensions" to join what they call a "Financial Fools' Day" targeting the banking elite on 1 April.
Organisers say they have seen a "groundswell" in support since the start of the recession and their Facebook site has attracted more than 1,000 members.
"There really is a shift because people feel no-one is listening - the government is in some world of its own," said one of the organisers, Camilla Power.
"Our aim is to challenge the legitimacy of the G20 summit."
But while G20 Meltdown insists its intentions are peaceful, the authorities fear other protest groups are preparing more disruptive tactics - such as attempting to enter banks and financial institutions - to fulfil their aim of bringing the City of London to a halt.
Protest expert Professor George McKay, of the University of Salford, says the economic crisis has served to boost support for such street protests this year because it has made criticising capitalism acceptable again - something that had all but disappeared in the 1980s and 90s.
"Here we are at an absolutely pivotal point," he says. "That, I think, will add to a new level of angry energy."
Cdr Bob Broadhurst, in charge of policing the G20, has said a £7.2m police operation is being launched, but has admitted security and protest are not "always happy bedfellows".
Only time will tell whether demonstrators demanding change and those defending the rule of law come into conflict once again.