premise: Hundreds of Climate Camp demonstrators - behind direct action protests at Heathrow Airport and power stations in North Yorkshire and Kent - have pitched tents in protest against carbon markets. Several hundred anti-war demonstrators are marching to a rally in Trafalgar Square from the US Embassy in central London. On Wednesday morning, protest groups under the G20 Meltdown banner had marched from Tube stations to the Bank of England urging those who had lost their homes, jobs, savings or pensions to join them in following four "horsemen of the apocalypse" to "lay siege" to financial institutions.
hypothesis: Trafalgar Square is in London.