Image copyright AFP Image caption Esmond Bradley Martin had risked his life to secretly photograph and document illegal sales of ivory and rhino horn 
 
 One of the world's leading investigators of the illegal trade in ivory and rhino horn has been killed in Kenya. The body of Esmond Bradley Martin was found by his wife Chryssee at their home in Langata on the outskirts of Nairobi with at least one stab wound in his neck, police said. The former UN special envoy for rhino conservation was known for his undercover work investigating the black market. Read: Inside China where smuggled ivory meets second death 
 
 Esmond, an American geographer, had been travelling all over the world with his wife, Chryssee Martin, and colleagues Lucy Vigne and Dan Stiles. His research, most of which was published by conservation group Save the Elephants, included a 2017 report that found that the Lao People’s Democratic Republic was home to the world's fastest-growing retail market for ivory, as well as a 2016 study that detailed how demand for ivory in Viet Nam was threatening elephants in Africa.
– "Pachyderms have lost a great champion." That's the tribute of one elephant expert for Esmond Bradley Martin, one of the world's most well-known ivory investigators, who was found killed in his home in Nairobi, Kenya, per the Telegraph and BBC. The 75-year-old had a stab wound to his neck, and investigators believe his death was the result of a robbery gone wrong. His wife says she went out for a nature walk and discovered his body upon returning home around 4pm Sunday, per the Star. Bradley Martin, identifiable by a colorful handkerchief he often had peeking out of his jacket pocket, was a major figure within the wildlife conservation movement who'd risen to prominence by going undercover, usually posing as a buyer, to expose the illegal market for ivory and rhino horn. A former UN special envoy for rhino conservation, Bradley Martin began his efforts in earnest in the 1970s, when the number of elephants being slaughtered for their ivory spiked. That's when he left the US for Kenya, and his work helped put an end to the sales of rhino horn and ivory in China. His travels also took him to Vietnam and Laos, where last year he and another researcher revealed the latter country's ivory trade was the fastest growing in the world. Their work there involved the dangerous ploy of pretending they were buyers and staying in a casino frequented by organized-crime members and traffickers, all so they could find out what the going price for ivory was. Local police say they've already questioned a cook and gardener at Bradley Martin's home and have come up empty so far on suspects.