By Ian Dunt
London has gone into lockdown ahead of what Scotland Yard is describing as the most challenging public order operation it has ever devised.
Delegates have been arriving for Thursday's G20 summit since yesterday, but tomorrow marks the first day of concern.
Angry crowds are expected around the Bank of England in an anti-banking protest, while environmental protestors are threatening to build a tent city in the middle of one of London's busiest roads.
One demonstration organiser said: "Their tax-dodging, bonus-guzzling, pension-pinching, unregulated free market world's in meltdown, and those fools think we're going to bail them out. They've gotta [sic] be joking."
A leaflet advertising the demonstrations read: "We should kick the bankers and political cronies out of the city and out of power. This is really the beginning of the end."
The Bank of England demonstration is the brainchild of G20 Meltdown, a loose coalition of Anarchists, environmentalists and anti-capitalists.
Climate Camp are organising the 'tent city' protest. They describe themselves as a national network of climate activists. They previously hit the news with a high-profile protest at Kingsnorth power station last year.
"First the city traders speculated with our homes, jobs and money - with disastrous results," a spokesperson said.
"Now they are speculating with our climate and the very future of life on earth - and once again our governments are cheering them on."
On the other side of central London, anti-war demonstrators are marching from the American embassy to Trafalgar Square.
"We're protesting the G20 because it's there that plans will be formalised to increase the number of troops in Afghanistan, which is a war that can't be won," a spokesman told politics.co.uk.
Police will then turn their attention to Wembley, where England play their World Cup qualifier against Ukraine in the evening.
Only after that will the security operation turn to the summit itself, as world leaders enter talks at the Excel centre, in east London's docklands.
Those talks have already had a tortured birth, with European leaders seemingly at odds with Gordon Brown and American president Barack Obama over the need for a further fiscal stimulus.
But protestors will be attempting to steal the spotlight on the day with Anarchist groups promising to knock on the doors of the centre.
The police operation to deal with the range of potential public disorders - called Glencoe - is estimated to have cost 84,000 police man-hours. All leave has been cancelled over the two-day period.
It will involve six different forces, headed by the Metropolitan police.
A spokesperson said: "The Metropolitan Police Service is monitoring all information relating to planned protests and advertised actions. We will have officers deployed at key locations plus a large number in reserve that can respond to deal with whatever takes place.
"We have been in liaison with a number of different communities in London including businesses to ensure that they have been briefed as fully as is possible as to what we are expecting."
But the Liberal Democrats warned police not to adopt heavy-naded tactics, and are sending a delegation of MPs to monitor the demonstration.
Liberal Democrat justice spokesman David Howarth said: "I was encouraged to hear the Metropolitan police talking seriously about proportionality when I met them today.
"I very much hope the that the rights of the protesters to make their important point peacefully will be fully respected."
politics.co.uk will be reporting from all the demonstrations as they happen, as well as bringing you all the news from within the summit on Thursday.