One of the mots embarrassing experiences that can happen to anyone is to meet old friends, and not recognize them. I once had to welcome a group of students at the airport. I knew the eldest person, a Madame Dufort, would be in charge of them, and when the group appeared, this woman came towards me, smiling, and said: "Doctor, what a pleasant surprise!)) If I had been quicker and more intelligent I would have said brightly: "How nice to see you, my dear!' as if she were my oldest friend, but I just stood there, my face getting redder and redder, trying to remember her. The worst thing about it was that she got even more embarrassed than I was, and said: "You don't remember me," still not giving me the slightest clue. Fortunately, my wife, who is more quick-thinking and better-mannered than I am, said: "Of course he does, Nicole, but he's the most absent-minded person in the world". Nicole had been a student of mine years before, but she looked much older, her hair was going grey, and her face had more lines in it than is usual at her age. She had got married, too, so her name was changed, and I find names easier to remember than faces.