From today’s Washington Post coverage of the G20 summit:

Earlier in the day, 11 people were arrested after being stopped in an armored personnel carrier in the financial district. The vehicle, which looked like those commonly seen on the streets of Baghdad or Basra, was painted blue with the word “Riot” stenciled on the front.
News photos showed at least one of the men arrested wearing a riot police officer’s helmet. It was not immediately clear how such a vehicle managed to drive into central London on a day when security levels are unprecedented.

Can’t imagine APCs get great mileage, particularly in the city. I hope those protesters bought sufficient carbon offsets.