GWEN MCILREE, THE 70-year-old widow of a carpenter, used to live in London Road, Croydon. In August last year her house was burned down and all her possessions, including her husband's ashes, were lost. She is sad for herself, but sadder for Croydon. I moved here nearly 40 years ago. It was a nice area. Why is there graffiti allowed all over the place? Nobody seems to care. The riots took everybody by surprise. They were not, it seemed, political or anti-police, but mainly about looting. Though they spread beyond the city, about two-thirds of the action was in London. Many explanations are offered. One set revolves around social conditions. Some people blame the politicians, claiming that the scandal over their expenses undermined public morality. Some blame the bankers, arguing that if people feel society is unfair they won't play by its rules. David Lammy, Tottenham's MP, thinks that "our housing estates have gone from being working-class communities to being workless-class communities with generations dependent on welfare and a significant minority on crime." The government-appointed panel that looked into the causes of the riots emphasised the effect of troubled families and the need for building character, "including self-discipline, application, the ability to defer gratification and resilience in recovering from setbacks." A second explanation focuses on policing. "The police were just standing there," says Bushra Ahmed, who watched the Croydon launderette her father bought 24 years ago burn down. The report of the Home Affairs Select Committee agreed: "The absence of a police presence or the sight of police officers apparently standing by and allowing criminal behaviour to take place was distressing for those whose homes and businesses were being attacked." The police admit that they should have got more officers onto the streets more quickly. A third explanation points to technology. BlackBerry Messenger, a service that allows users to broadcast messages free to all their contacts, was used by rioters to summon their friends to join looting sprees. Just as in the Arab spring, the security forces, which used to have superior communications, found that technology has shifted the balance in favour of the street. A fourth explanation fingers the physical environment. Tim Stonor of Space Syntax, an urban-design consultancy, points out that the vast majority of the riots took place within a five-minute walk of one of the depressing post-war housing estates which councils are now pulling down. The fifth explanation blames London itself. "Rioting is something that London does," says Tony Travers, director of LSE London, a research centre at the LSE. There were riots in 1809, 1816, 1830, 1866, 1886, and so on. Given that the population has increased by one-and-a-half million in the past 25 years, and two-and-a-half million people in this city were born in other countries, some of which are at war with each other, it is a miracle the place is as peaceful as it is.