It is true the police will have a large presence. And many will indulge in aggression given the chance. There will also be agent provocateurs, plain clothes police and private security guards.
The notion that all organisations are infiltrated is a misnomer. We are all in this together. All mobile phones are living bugs, giving som iea of location (nearest transmitter), and the authorities are well aware of all the key players involved.
Alcohol will not help anyone, being alert will! Don’t be goaded or provoked, be wary of entrapment (A fake fight for example, to which you feel compelled to intervene), be wary of a group of agent provocateurs running down the street in a (false) state of panic trying to stampede everyone.
Be ready for the police to cordon whole groups of people into a confined space for hours. There is advice here:
I think tubes and buses are likely to be canceled, traffic jams will be created, people will not be able to rendezvous, bicycles are reliable.
The authorities have decades of experience, and also call upon experts from other countries.
Here is an excerpt from another blogger:
Apart from the protesters, though, the people who will really be having a ball next week are the heads of security at the City’s large corporate buildings. Many of them are ex-army or ex-police and often they tend to feel ignored and undervalued for much of the year. But next week will be their time in the sun. During the last major protest, I remember our security staff mounting a military style operation. They had set up communications with the police and with other security officers in other firms. They had a map on the wall where they plotted the movements of various protesters. As I stood talking to one of the guards in reception, on his radio he was getting regular updates on where the protesters were. I remember him telling me that McDonald’s on Holborn had been trashed. It was all very impressive. No doubt the security staff at all the major London offices are already preparing for war. They will probably enjoy themselves as much as the protesters.
In my experience, these anti-City protests are never as bad as they are hyped up to be. I expect there will be a lot of noise next week and some isolated violent incidents but I would be surprised if the mayhem gleefully predicted by the media actually comes to pass. –source–