Fourth-century Europe seemed prosperous, stable and secure. In that well-connected world, local communities often flourished. But this came to a sudden end in the fifth century. Both global connections and local societies were disrupted; an era of poverty and violence began. (And the climate got worse). Nobody then had foreseen the catastrophe; but hindsight shows slowly building imbalances reaching a tipping point. What imbalances? What tipped them over the edge? What was it like afterwards? And what happened in Britain?