Namdeb feeds the ore to its mill, which crushes, sifts, and washes it, leaving a gravel concentrate. A large population of single men with lots of spare time to think up ways to steal diamonds thus permanently occupies the most sensitive area of a famously rich mine. Miners with luggage pass in and out at will. Criminal syndicates, active at mines throughout the region, conduct a brisk bourse inside Namdeb's hostels. Nor is money the only incentive.
Coercion is ubiquitous.
Once that gets in place, it's very hard to eliminate. Reluctant to offend the Namibian government, Namdeb will not raid the hostels. A few years ago Namdeb's beleaguered security force tried a different tack. The thinking was, if we can't do anything about the hostels, let's stop the buses on the way back. So without warning, security stopped the buses.