It has happened again.
The death of Ian Tomlinson at last April's G20 protest would surely have been covered up by the police, were it not for the bravery of the person who filmed the incident and posted the footage both to the media and onto the web in general.
Now we hear that footage exists on YouTube from last week's student demo, of a guy being pulled out of his wheelchair and dragged across the road by a policeman.
It is very sad that these things happen, but it is wonderful that mobile phones have evolved to such an extent that it is easily possible for people to record such evidence at the drop of the hat, meaning that it is far harder for the police to cover up the criminal actions of individual officers (although I note that the guy whose blow killed Tomlinson was never charged).
The politicians talk about "consensual policing" but exactly how much respect do they think the public will have when they log onto the web and see what some of the thugs dressed up in uniform get up to?