I have a vague recollection of Mike Tyson announcing himself as the undisputed champion of the world and being put in his place by an elderly British scientist. Who was the scientist and what was the exact exchange?

I have since rediscovered what this was about.
It wasn't a scientist, but was an English professor of philosophy, AJ Ayer.
In 1987, Mike Tyson was harassing a young Naomi Campbell, and when Ayer asked him to stop, Tyson turned to the professor and said:
"Do you know who the f*** I am? I'm the heavyweight champion of the world,"
Ayer replied: "And I am the former Wykeham Professor of Logic. We are both pre-eminent in our field; I suggest that we talk about this like rational men."
Meanwhile, Naomi made the most of this chance and slipped away.
https://www.theweek.in/webworld/features/society/a-j-ayer-the-philosopher-who-supplanted-god-bested-mike-tyson-by-words.html