Imagine a world where a single commodity holds the power to unravel an empire. A substance that is so strong, so addictive, it courses through the veins of a whole civilization, making merchants into monarchs, emperors into desperate bargainers.

This is the story of opium in China - a story not just of drugs and war, but also of greed, diplomacy and unintended consequences.

If we take the long view, 19th century China was an altogether self-sufficient superpower. The Qing Dynasty, with its inflexible traditions and isolationist practices, ruled over a formidable and prosperous empire. Chinese silk, porcelain, and, most of all, tea were in high demand in Britain.