Britain’s police knew they were in for a difficult weekend. On July 29th three children were murdered in a dance class in Southport. False rumours that their killer had been Muslim and an illegal immigrant who had arrived in a small boat quickly spread across the internet, leading to a riot in the northern town on the following day, as well as violence in London, Hartlepool and elsewhere. Sir Keir Starmer, Britain’s prime minister, decried the unrest as the work of a “tiny, mindless minority” of “thugs” on the “far right”. Further demonstrations across English cities on August 3rd reinforced that verdict but also revealed a wider, inchoate sense of grievance.