“John Banville Kills Off a Pen Name: Snow would normally have been published under the pseudonym Benjamin Black, but Banville says he doesn’t need that ‘rascal’ anymore” — The New York Times

https://www.nytimes.com/2020/10/01/books/john-banville-snow-benjamin-black.html

I need not explain to readers here that Black is Banville’s alternate personality, but The New York Times may never get it.

Added Oct. 19, 2020: Search "Greene's novella" to see how Graham Greene started his novella for The Third Man with a description of a fictional author who had two personalities that published under different names.