Wilderness of Mirrors by Linda Davies

Two women - once friends at Oxford - and a diamond mine in Vietnam are the bait that M16 hope will ensnare businessman-villain Robie Frazer. Frazer's business interests are multi-national and his wealth extraordinary. But he has become corrupt, selling arms to the Chinese, extorting what he needs from people by violence and blackmail. Eva Cunningham, undercover agent-turned-heroin-junkie, has reason to hate Fraser And her old friend Cassie Stewart, now a high-flying venture capitalist in the City, also finds herself involved in the game to trap Frazer. A game which will end in a terrifying hunt-to-kill pursuit in the jungles of Vietnam.