A global workforce. Billions in sales. But, unlike Tesco or BP, few have heard of it. The Cartel is Britain's biggest drugs organization, a shadowy network stretching from the freezing, foggy banks of the Mersey to the glittering marinas of Marbella, from the coffee shops of Amsterdam to the trading floors of Canary Wharf. On the bottom rung, there are street gangs who dress in black North Face jackets and are armed to the teeth. At the top, there...