Even before the dam collapsed, Lamec did not feel safe working at the copper mine. “If our work protective gear gets damaged, it is not always replaced,” he tells us. “We have to take a risk and use it again.” He is talking to the BBC in a car on a quiet backroad near a village in northern Zambia, too nervous to speak to us in public or to use his real name, for fear that speaking to the press might cost him his livelihood. When he turned up for his shift one day in February, he tells us, he found that one of the dams at the Chinese-owned mine had been closed. The tailings dam – used to store...