Some will dress as clowns, others will wear masks, some will even be carrying their own environmentally friendly compost lavatories. But all are intent on bringing chaos to London.
After days of speculation and intensive planning, central London is bracing itself for 48 hours of protests and chaos as thousands of demonstrators from a plethora of different causes descend upon the city for the start of the G20 meeting of world leaders.
Anti-capitalists, social justice groups, environmental activists, anarchists and anti-war protesters have all vowed to hold a series of demonstrations across London as 20 of the world's most powerful leaders meet to try to find a way out of the global economic crisis.
As major world players such as Barack Obama and Dmitry Medvedev are ferried around town in armoured limousines with police escorts, demonstrators have vowed to make their voices heard through a series of carefully orchestrated stunts designed to capture the most publicity.
The City of London, which is widely seen by many protesters as the place where the credit crunch began, will be the focus of two mass demonstrations today. Tomorrow protesters will turn their attention to the ExCel Centre in Docklands, east London, where the summit is being held.
A coalition of environmental activists have vowed to defy police barricades and set up a "Climate Camp" outside the London carbon-trading exchange, ECX, off Bishopsgate at 12.30pm today. If they succeed, numerous roads in the City will almost certainly be closed. Previous climate camps have been held in fields outside Heathrow airport and Kingsnorth power station in Kent.
Anti-capitalist protesters and those angry at the Government's recent bailouts of the banks are holding a series of marches from four Tube stations which will converge on the Bank of England today at noon. The G20 Meltdown coalition group, which is organising the marches, has vowed to hold a "Banquet at the Bank", at which effigies of those in the financial centre will be burnt.
One of the most expensive policing operations in the capital's history will see more than 2,500 police officers on hand to make sure that the demonstrators remain peaceful. All leave has been cancelled and officers will be coordinated by up to 3,000 CCTV cameras monitored from a specialist operations room in Lambeth. Commuters have been warned to expect delays and many City employees have been either told not to go into work or to dress down to avoid any confrontations. Transport for London is not intending to shut any Tube stations but police will have the power to close roads and stations if things get out of hand. Many bus routes are likely to be heavily affected.
Numerous environmental and anarchist groups are expected to resort to small acts of direct action away from the main protests which may lead to further travel delays. There are also likely to be road closures in and around central London today and tomorrow.
Yesterday environmental activists in Whitechapel were fine-tuning their plans to install the climate change camp in the City. James Holland, a 36-year-old activist, said he hoped the police would not try to stop the camp from being set up. "I think it would make the police's job a lot easier if they just let us set up the camp," he said. "At least that way we would all be in one place. Trying to stop us would be a colossal waste of time because we'll just go somewhere else if they don't let you go outside the carbon exchange."
In a squat off Commercial Road in east London, a collective of European anarchists were also planning their marches. "The next two days will be a lot of fun," said an Italian activist. "A lot of fun."
Q&A: Everything you were afraid to ask about the G20
G stands for Group, and 20 is supposed to be the number of countries taking part. Actually, there are 22 – but don't ask. Together, they represent around 90 per cent of global gross national product, 80 per cent of world trade, and two-thirds of the world's population.
Where can I see Barack Obama?
On television is your best bet. He and Michelle spent last night at the US ambassador's official residence in Regent's Park, and he will travel to his various engagements in Cadillac One, so you can try waiting on his route in the hope that he will wave. The couple have a private audience with the Queen this afternoon, followed by a reception for all the G20 leaders. Then they go to 10 Downing Street for a working dinner, which starts at 8.30pm. Jamie Oliver will be their cook.
What about the wives and husbands?
While the leaders dine and talk politics, their wives will be having a more relaxed dinner next door at No 11. And it will be wives, because although G20 includes two female heads of government – Germany's Chancellor Angela Merkel, and Argentina's President Cristina Fernandez de Kirchner – neither husband is tagging along. A number of famous British women will join them at dinner. Sitting on either side of Michelle Obama will be the author J K Rowling and the double Olympic gold-medallist Dame Kelly Holmes.
Which wife will steal the show?
Carla Bruni Sarkozy will not be there, which pretty much leaves the field open to Michelle Obama. Her only competitor in the glamour stakes is the opera singer Sonsoles Espinos, wife of the Spanish Prime Minister Jose Luis Rodriguez Zapatero.
G20 in numbers
275 The exact number of minutes the formal talks will last.
1,000 The number of translators and security guards accompanying the 500 delegates.
3,000 The number of CCTV cameras in London that police will access to monitor security.