...the police encourage chaos by threatning to kettle people – at every demo now, people are premptively breaking out of agreed protest routes whenever there’s the slightest whiff of a kettle about to be set up. Ironically, the threat of kettling has served to make protests more unpredictable, and less easy to control for either police or organisers.
I think he is probably right. Detaining people in freezing weather for several hours for no other reason than that they are on a legal protest is not exactly the best way to promote good relations between police and demonstrators. It is pretty clear that in these circumstances, the police see themselves as the last line of defence against the anarchist hordes. Since those 'anarchists' are inside the country they are become more and more an occupying force and not, as Robert Peel would have it, as being members of the same public as the protestors.