Nguyen Tien Tung is just the sort of man you'd expect to run a Hanoi slaughterhouse: wiry, frenetic and filthy, his white T-shirt collaged with bloodstains, his jean shorts loose around taut, scratched-up legs, his feet squelching in plastic sandals. Hunched over his metal stall, between two hanging carcasses and an oversized tobacco pipe, the 42-year-old is surveying his killing station – an open-air concrete patio leading on to a busy road lined with industrial supply shops.