In the interests of research, I have taken a jar of pickled gherkins out of my fridge and examined them closely. They do not look much like the new circular, tapering Lord Foster skyscraper at the epicentre of the City of London. They have blunter ends, tend to curl somewhat, are covered with warty excrescences, and are green. Foster's 30 St. Mary Axe tower, to give it its official name, is too sleekly, darkly, fatly mechanistic to be confused with your average cucumber-related fridge vegetable. But in the popular mind it is, and probably always will be, the Gherkin. Let's not fight it. Let's embrace it.