Why did police charge only 11 rioters over the anti-cuts protests?

Of course they mean AT MOST 11 rioters, since all but 11 definitely had nothing to do with any rioting. That's not to say the other 11 were involved either. The police had to charge 138 people over the Fortnum and Mason protest because it would have looked really bad if the headline the next day had been 'only 11 charged', and most people don't notice that the vast majority charged had nothing to do with any violence or damage.