With the delights of San Francisco behind us, we drive into the town of Napa just before lunchtime on that most significant of American days, the fourth of July. Stars and stripes are very much in evidence, bunting and banners adorn the streets and there is a sense of anticipation in the air. The River Napa which flows swiftly through the town and runs directly into San Francisco Bay, once supported heavy industry here, until alternative forms of transport took away its water borne advantages and Napa and its neighbours suffered a downturn. What followed later wasn’t quite the Gold Rush of 1849 but you could conceivably call it the…