"Sunglasses must be kept on until an acquaintance is identified at one of the tables, but one must not appear to be looking for company. Instead, the impression should be that one is heading into the cafe to make a phone call to one's titled Italian admirer, when--quelle surprise!--one sees a friend. The sunglasses can then be removed and the hair tossed while one is persuaded to sit down."
— Peter Mayle (A Year in Provence)