All serious visitors to Rome have a place that they always considered their personal find, but whose existence is inevitably revealed to the world at large, with a resulting change in ambience. Mine is Ristorante Pietro Valentini, just a few steps from the Hotel Portoghesi, where I have often stayed. This is the classic establishment of its sort – family run, and exactly seven tables in the place. But what set Pietro’s apart has always been the quality of the food and the supreme friendliness of Simona, the daughter-in-law of the family, who manages the room. Since the last time I was there the Internet had taken up the restaurant, and indeed some things were different on this trip. An American couple sent there by the concierge at the Excelsior sat in front of me. That did not bother me as much as the absence of two rituals that opened a meal at Pietro’s...