Anonymous Call Girl Author Belle de Jour Outed as 'Slutty Scientist' Costume Incarnate Foster Kamer · 11/15/09 05:45PM Showtime's Secret Diary of a Call Girl was based on a series of bestselling books by anonymous prostitute Belle de Jour. How hot is this? Turns out she's a well-regarded British scientist, Dr. Brooke Magnanti. She came out last night.