It started as a Labor Union protest of the budget cuts in the UK, but then the anarchists added their special touch.
Yes the UK is broke, and has to cut the budget. The parasite class, is expecting money to fall from the sky (same as in Greece) to fund the dependent lifestyle to which they have become accustomed.
Anarchists utilized the opportunity to tear up the Ritz Hotel, and other landmarks of central London.
More pics and a timeline are available at the the Telegraph.