The rise of urban terrorism is not a departure from recent European history but a return to the norm. The exceptional period was the late 1990s, when there was relative peace in our cities. But before then, various political groups regarded the slaughter of innocent civilians as a legitimate political tactic. When one lumps that in with the rest of 20th century European history – the Great War, the Spanish Civil War, the Holocaust, East European red terror and the violent breakup of Yugoslavia – our corner of the world starts to look a little less civilised than we tend to think. And recent history, a lot happier.