Police warn protesters on Million Mask March in London

Supporters of Anonymous, the anarchic hacking collective, will wear Guy Fawkes masks at the event in central London, which starts at 6pm. Last year's event in London erupted in violence with missiles and fireworks thrown at police, injuring four officers and six police horses. Ahead of the event, Metropolitan Police Commander BJ Harrington said it was apparent that some only went along "intent on criminality".