Traditional psychological explanations of crowd theory have decontextualised eventsand obscured the fact that crowd incidents are typically inter group encounters. Thishas led to research being rooted in the crowd whilst ignoring the other parties whomay be present - including the police - and how events develop as function of theinteraction between the two. The studies reported in this thesis attempted to provideinsights into the decision making of senior public order officers of the MetropolitanPolice utilising a variety of qualitative and quantitative methodologies. Four mainstudies are reported. In the first study (of police training) a grounded theory analysisrevealed that the police have a fear of the crowd which is seen in a concern withprovoking violence by being too harsh or permitting violence by being too lenient. Thebalance of harshness and leniency is informed by accountability considerations arisingfrom internal and external sources and the phase of violence the officers perceivedthemselves to be in. In the second study, the relationship of accountability and phasewas manipulated in a controlled experimental setting providing supportive evidence forthe grounded theory model. The third was a series of pilot participant observationstudies which looked at the policing of the Muslim festivals of Eid al Fitr and the Sikhfestivals of Vaisakhi. These studies raised practical issues and was used in designingthe fourth study which looked at the 'in vivo' processes of decision making during thebiggest public order event in London of 1999. This confirmed and extended the focuson the importance of accountability concerns in senior officer decision making; firstlyby showing them to be more complex than was originally thought, secondly byshowing how those in different positions within the police had different accountabilityconcerns, and thirdly by showing that such different concerns could lead to conflictbetween different sections of the police. The implications of this research and thefoundations of future research are also discussed.