The Golf is six years old, twice the age of the somehow far less popular Opel/Vauxhall Astra. Ford of Europe's new Focus ought to be pummeling its elderly rival but that isn't happening either. Toyota, Hyundai, Peugeot, Renault, Kia - the list of major makes selling cars in the C segment which Volkswagen's long-time king stays ahead of is long. What is the Golf's secret?