I’ll have to flip through the book and see if Campari appears anywhere else in it.
He has a couple more drinks with Campari, including one called The Tunnel (equal parts gin, Campari and a sweet / dry vermouth split). His previous book (1943, I think) featured the Camparinete (from ‘Albert, Chatham’).
It pretty much fit Dave’s chronology. Sanfeliu Brucart was very well travelled and very connected, so it’s not a surprise that he would have been of the first to feature a Negroni.