In August 2011, several areas of London experienced episodes of large-scale disorder, comprising looting, rioting and violence. Much subsequent discourse has questioned the adequacy of the police response, in terms of the resources available and strategies used. In this article, we present a mathematical model of the spatial development of the disorder, which can be used to examine the effect of varying policing arrangements. The model is capable of simulating the general emergent patterns of the events and focusses on three fundamental aspects: the apparently-contagious nature of participation; the distances travelled to riot locations; and the deterrent effect of policing. We demonstrate that the spatial configuration of London places some areas at naturally higher risk than others, highlighting the importance of spatial considerations when planning for such events. We also investigate the consequences of varying police numbers and reaction time, which has the potential to guide policy in this area. T he need for public policy to be informed by an evidence-based approach has been recognised for some time; however, this is often problematic, particularly in the context of rare events. The difficulty is especially evident in situations where quantitative recommendations are required, such as estimating the appropriate contingency for a certain scenario, since traditional hypothesis testing is undermined by the paucity of data. In such cases, mathematical modelling has much to offer, allowing rigorous quantitative analysis of the system in question and the testing of varying scenarios. Recent advances in the modelling of large-scale social systems using techniques of complexity science mean this is now a viable approach, and indeed its potential has been demonstrated in such fields as epidemic modelling 1, 2 , crowd control 3 and infrastructure resilience 4 . Here, we employ such an approach in the context of the 2011 London riots and the policy questions subsequently arising. The London riots occurred between 6-10 August 2011, as the UK experienced its most widespread and sustained period of civil unrest for at least 20 years. Repeated episodes of looting, rioting, arson and inter-personal violence took place in several cities, including London, Manchester and Birmingham. The consequences of the events include numerous instances of injury, including five deaths, and extensive property damage, for which liability has been estimated as £250 million 5 . Here, we focus on the disorder in London, the worst-affected city. The London riots have been the subject of much research in the academic 6 , governmental 7 and journalistic 8 communities. The majority of this research, however, as with much of that considering previous episodes 9 , has focussed on the psycho-social motives of individual rioters, ascribing willingness to participate to various social factors, including unemployment, poor police relations and endemic criminality. Our work is distinct from this; rather than consider how and why the riots began, we take their initiation as our starting point and instead consider their spatio-temporal development. This approach is informed by the policy question which motivates our work: how, once such an incident is in progress, the police might best respond in order to suppress disorder as quickly as possible. Several questions relating to the response of the authorities were raised following the disorder. Although order was restored after five days, it has been variously claimed that the police were inadequately prepared and slow to react to developments, and that disorder might have been suppressed sooner; indeed, official inquiries have acknowledged such shortcomings 5, 10, 11 . Alongside a need to anticipate better the disorder itself, these inquiries have emphasised the need to establish a level of policing resource, and mode of response, commensurate with an outbreak of this magnitude. Mathematical modelling can contribute to this by allowing quantitative examination of the effect of varying police responses, and the investigation of a range of scenarios. A crucial factor in determining police response to a riot, and indeed for policing in general , is an understanding of the spatio-temporal distribution of events. The London riots are notable for the fact that, despite being apparently catalysed by a specific incident -the fatal shooting by a police officer of a suspect in Tottenham, North
Similarly, REF examined the spatial development of disorder against the effect of varying policing arrangements as occured in London riots in 2011.
A mathematical model of the London riots and their policing
Scientific Reports
Scientific Reports
Medicine Sociology