The battle to save the African rhinoceros has all the ingredients for a Hollywood thriller. There are armed baddies with good guys in hot pursuit. There is a hint of glamour. And the drama is played out against a backdrop of a beautiful, bloodstained landscape.

It is a story that begins, perhaps improbably, in Vietnam soon after the turn of the 21st century. A Vietnamese official of some influence, so the story goes, lets it be known that he, or perhaps it is his wife (for the sake of the story it matters little), has been cured of cancer. The miracle cure? Rhino horn powder.

With disconcerting speed, the story shifts to southern Africa, where a series of gunshots ring out across the African plains. This is followed by the hacking sound of machetes - it takes little time to dehorn a rhino because its horn consists not of bone but of keratin fibres with the density of tightly compressed hair or fingernails.

The getaway begins, armed rangers give chase. Once the horn leaves the flimsy protection of the national park or game reserve, where its former owner lies bleeding to death, it may never be found, its new owners never brought to justice. Sometimes they are caught. Sometimes they get away. Either way, another rhino is dead in a war that the bad guys seem to be winning.

The story shifts again, back to Vietnam where even the prime minister is rumoured to have survived a life-threatening illness after ingesting rhino horn. More than a cure for the country's rich and powerful, however, rhino horn has by now crossed into the mainstream. Young Vietnamese mothers have taken to keeping at hand a supply of rhino horn to treat high fevers and other childhood ailments.