The Bay of Arcachon, on the south-west coast of France, is a happy place. It must be, because I’ve been visiting it with my family nearly every year for the past 15 years. We usually rent a small apartment in Arcachon town for four or five days, but such is the draw that we have been known to make a two-hour drive just to spend the day there when we’ve been in that part of the world. Everything about it speaks of summer joy: the promenade thrumming with cyclists and strollers; the parade of bistros serving moules, oysters and buckets of chilled rosé; families playing beach tennis on the sands; and a bay brimming with pleasure boats and ferries. It’s like a scene from a Raoul Dufy painting.