Face Blindness
Some people never forget a face. Some never recognize one. Most of us are somewhere in between these extremes.
I remember a character in a movie who said, "I never forget a face." He said this to the bad guy, who had been a guard in a Nazi concentration camp. Eventually the bad guy killed him to prevent his past from being exposed. (I don't remember the name of the movie.)
At the other extreme are people like Oliver Sacks, who can't even recognize their closest relatives. They are said to suffer from prosopagnosia or face-blindness. Apparently this is caused by a lesion in a certain part of the brain.
After the main character in the movie "Faces in the Crowd" witnesses a murder, the bad guy attacks her. She falls and hits her head. After that, she is face-blind, to the extent that she can't recognize her father or her boyfriend. The killer knows who she is and worries that she might recover and be able to identify him. She has other problems as well. Her boyfriend dumps her because he can't stand not being recognized by her. She was a schoolteacher, but ... (I won't say more, so as not to spoil the movie).
I can relate to the main character in that movie, because I have always had difficulty recognizing faces. I can recognize people I have known for a long time, but get confused about the identities of casual acquaintances. To some extent I can compensate by recognizing peoples' voices, gaits, hair styles, and other features. But I would be a lousy schoolteacher. In fact, most jobs require more ability to recognize faces than I possess. I have only recently realized the extent of my limitation.
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I thought I was below average on face recognition. It must be something else.
Perhaps I do recognize casual acquaintances, but I lack confidence that I really know them, and am too shy to risk speaking to the wrong person. 
"Some British guy"
Somehow I knew that much.
