Yesterday outside London University there were lots of excited groups of teenage/school-age boys with face masks, and within minutes of the march heading off some of them started breaking away from the main demonstration, at a run, into the side streets of Covent Garden.
The permits issued by the authorities for the protests specify that the main demonstrations are to be held far from the White House, the Government headquarters, which is still a potent emotional symbol for the left.
Ahead of the main demonstration, an attempt to blockade Mexico City's airport by a few hundred protestors was abandoned after a large contingent of riot police blocked their way.
About 20,000 police officers were due on duty to watch over the main demonstration, but that number is likely to rise in the coming days, with two major marches planned for Saturday expected to draw crowds of up to 100,000 people.
The security forces eventually moved closer to the main demonstration area in front of Sana University, where people have been protesting since the uprising against President Ali Abdullah Saleh began in February.
Three local Orange lodges alongside about 100 supporters are being allowed to pass by the nationalist Ardoyne on their way to join the main demonstration in Belfast city centre.
While the main demonstration passed off peacefully, several hundred protesters tried to break through police cordons around the seat of the Spanish government in the city.
London's Deputy Mayor Kit Malthouse said officers had a "difficult balance" to strike between policing the main demonstration and unrelated incidents of violence including attacks by anarchist groups.
But London's deputy mayor Kit Malthouse said officers had a "difficult balance" to strike between policing the main demonstration and unrelated incidents of violence including attacks by anarchist groups.
After coordinating a companion Million Mom March in that city, she brought her family to Washington this weekend for the main demonstration.
