In the Mexican War on Drugs, the word, “cartel” gets thrown around a lot. The Sinaloa Cartel; The Gulf Cartel; La Famillia; Los Zetas. But who actually are these organisations which have inflicted grotesque violence on Mexico – and made billions of dollars in the process? How did they grow from small smuggling gangs, to mighty empires – and then splinter into separate factions each fighting one another?