I love Orson Welles at his wittiest. I have become a Negroni addict, but I never researched the history until now. Wikipedia, that most reliable of sources, offers the following tidbit:
One of the earliest reports of the drink came from Orson Welles in correspondence with the Coshocton Tribune while working in Rome on Cagliostro in 1947, where he described a new drink called the Negroni, "The bitters are excellent for your liver, the gin is bad for you. They balance each other."