Billions in sales. But, unlike Tesco or BP, few have heard of it. The Cartel is Britain’s biggest drugs organisation, a shadowy network stretching from the freezing, fog-banks of the Mersey to the glittering marinas of Marbella, from the coffee shops of Amsterdam to the trading floors of Canary Wharf. Run by godfathers as rich as Branson but kept in line by a new generation of teenage killers. Here is the inside story.