Yesterday, I watched as hundreds of Londoners took to the streets in a heroic attempt to clean up the mess caused by rioters and looters the night before. Looking at pictures of large crowds getting off trains with cleaning equipment in hand and marching down streets with brooms held aloft, I’ve rarely felt so proud of my city.

The clean-up operation was a great move – a positive note in an otherwise depressing week and a chance for a beleagured capital to come together and reclaim its sense of community. But the act of cleaning away the preceding day’s damage was also important. To explain why, I’m reposting this piece from a few years back about a Dutch study which showed