Thetford, England, population about 25,500, has been mostly quiet since King Henry VIII’s dissolution of the monasteries kneecapped the local economy in 1540. But several nights of violence last week put the Norfolk market town in the news. Crowds angry at plans to house asylum seekers at a nearby Royal Air Force site attacked buildings where migrants were believed to be sheltered. An uneasy peace returned over the weekend, but British authorities worried that the antiforeigner violence could spread. Thetford is only one place where migrants—and locals’ resistance to mass immigration—are making headlines.