From the Texas-Mexican border the Pan-American Highway snakes down through Central America and some of the world's poorest and most troubled countries. "To be perfectly honest, I was dreading this trip", declares the poet Hugo Williams as he sets off on a 3,000-mile drive through chronic political violence, weird religious practices and some of the hottest music in Central America. He finally comes to a standstill in the jungles of the Darien Gap, where the highway becomes a dirt track and Texas seems a long way away.