A constituency of similarly located people must come to see themselves as a group sharing common grievances. These are articulated in terms of a set of beliefs that justify their public expression by means that deny the legitimacy of the rules and restraints of normal conduct but which can be presented in terms that generate or maintain public sympathy or support. Once a group of people is prompted to express grievances collectively, the likelihood of disorder appears to depend on whether the aim is expressive or instrumental. Expressive symbolic protest is rarely associated with public disorder except where the aim is to express displeasure with police or other security forces. Instrumental protest, by contrast, is almost always disorderly. Most protests do not evolve into public disorder because the majority of people acknowledge the legitimacy of the State and its agents. However, this legitimacy is always contestable: what may be seen as legitimate maintenance of order also may be viewed as the oppression of minority rights. Thus, both police and protesters must attempt to appeal to a wider audience: rioters wish to convey an image of police oppression, while police seek to maintain the legitimacy of their authority. Consequently, dealing with a riot is not merely a matter of devising effective tactics, but of acting in a way that will appeal to the wider audience. It is in this regard that police have failed.