As dear Erasmus said in De Civilitate, “It is safe to admit nothing that might embarrass one if repeated.” Gossip - Judith Martin

She expects you to keep your eyes still while you say to the conductor, “Of course, I’d be glad to, but I especially wanted to sit by the window. Would you be good enough to find me another window seat? And then we could change.

One can become quite proficient at this amiable patter; the trick is to omit the instructive parts when attending formal dinner parties outside the house. It would be a mistake for Miss Manners to provide you with a list of no-no’s. It may never have occurred to your children to laugh with a mouthful of soup, for instance, or to discharge unappreciated salad ingredients into the napkin. Here, instead, are a few yes-yes’s: Small

The correct British peer would no more dream of using his own title than he would of using his own umbrella, although he carries both and is proud of their age.