Mr Chivers overlays a street map with colours representing the different substrata - " half eccentric artwork, half primary-school science project" - which becomes a springboard for his digressions.
When I get a score report from a student and it says writing 12 points or it says independent writing 1.0, I know it's almost guaranteed they got flagged as being off-topic.
He always gets sidetracked on tangents, but the way that he just sort of gets consumed by them now, he'll just be saying one thing and then he'll kind of forget completely what he's saying.