Shanghai, like most Chinese cities, has a small core of disgruntled citizens who regularly congregate outside public buildings in the hope of getting officials to hear their complaints. Many are unemployed or retired and feel they have little to lose by challenging authority.

Over the past few weeks, however, their sense of injustice has risen as details have dripped out about a scandal at the Shanghai government pension fund, which on Monday led to the dismissal of the unloved party secretary, Chen Liangyu.