New analysis led by a Sussex psychologist has explained the way in which the 2011 riots spread – something which may be useful for policy makers in future.

Professor John Drury at the University of Sussex, who is an expert in crowd behaviour, led a team of academics from Sussex, Keele and St Andrews universities to analyse data and accounts from the 2011 riots in England.

The authors found that there were essentially three stages to the rioting:

• Firstly, two days after Mark Duggan was killed, a protest against the police turned into a riot in Tottenham.
• Secondly, the riots spread to a small number of areas in London, including Brixton. A close analysis of the data and accounts shows that Brixton participants often identified with Tottenham – as two areas share a history of rioting over police racism. People in Brixton were therefore influenced to riot out of anger and a sense of injustice at the killing of Mark Duggan
• Thirdly, the riots in Croydon and Clapham were more influenced by the perception of police vulnerability across London and an underlying anti-police sentiment in these areas. Deprivation in all these areas was a leading factor.

Professor Drury, from the School of Psychology at the University of Sussex, said:

"While previous research has shown anti-police feeling among the rioters, what we have now found is that the rioters used their views of the police to define themselves collectively. Their sense of identity was key. Knowing and seeing others feeling the same way, across various locations, made the rioters feel that they were not alone, and emboldened them to riot too."

The authors compared London boroughs that saw rioting with those that did not. Deprivation was the strongest predictor of whether a riot occurred in a London borough. There were significantly greater numbers of deprived people in the boroughs that saw rioting than in those that did not see rioting. In addition, the greater the number of deprived people in a borough, the greater the number of recorded riot offences in a borough and the longer the duration of rioting within a borough.

The boroughs which had more 'Stop and Searches' in the two-and-a-half years before the riots were more likely to see rioting in August 2011. To illustrate this point, the authors looked at population-adjusted average numbers of 'Stop and Searches' in 2010. In the boroughs that saw rioting the figure was 8,442 per 100,000 population, which was more than double the average number (4,141) for those boroughs that didn't see rioting.

Attitudes to policing were measured in a 2011 Metropolitan Police Service (MPS) survey that sampled 9,660 people in all the London boroughs in the months before the August riots. Those boroughs in which people saw the police negatively and felt alienated from them were those that later saw the most rioting.

The research also busts myths about the riots, including:

• The media often talk about a riots being caused by any "spark". In fact, there was no single "spark" for the riots. Instead they occurred after a drawn-out process. In each location, conflict with police and power-reversal in a local deprived estate was often the point at which smaller skirmishes became a mass event.
• The idea that those who rioted were mainly convicted criminals is not supported by official Home Office data. That myth is believed to have arisen because those are the people who the police arrested first.
• The riots occurred in waves, but not everyone who was exposed to them joined in; they were not simply "contagious".

Professor Clifford Stott, Director of the Keele Policing Academic Collaboration (KPAC) at Keele University, said:

"Our report represents a major breakthrough in understanding how and why riots develop and spread from place to place.

"The riots were not 'mindless criminality' and 'copycat rioting' but complex processes involving shared anti-police identity among the rioters and forms of empowerment that appear to have emerged during the riots as a function of interactions with police.

"It's important to understand that our goal is developing partnerships with policing partners so that they can learn directly from our world-leading research.

"In building scientific explanation, we are not diminishing the seriousness of what happened or are we blaming the police. Our report simply highlights the need for an evidence-based approach and we hope the lesson will be learnt as a consequence of our project that helps prevent similar riots in the future."