It took hundreds of years before the population was restored to Roman levels. If we think that no such disaster could happen again, we are not just arrogant but forgetful of the lessons of the very recent past. Never mind the empty temples of the Aztecs or the Incas or the reproachful beehive structures of the lost civilisation of Great Zimbabwe. Look at our own era: the fate of European Jewry, massacred in the lifetimes of our parents and grandparents, on the deranged orders of an elected government in what had been one of the most civilised countries on earth; or look at the skyline of modern German cities, and mourn those medieval buildings blown to smithereens in an uncontrollable cycle of revenge. Yes, when things go backwards, they can go backwards fast. Technology, liberty, democracy, comfort – they can all go out of the window. However complacent we may be, in the words of the poet Geoffrey Hill, “Tragedy has us under regard”. Nowhere is that clearer than in Greece today.