Well, that first course was very basic and open to all students, and I didn't know who he was. Just seemed like a typical lecturer way down the front of a big hall.
A couple of years later, he taught my class of ~20 his Calculus of Communicating Systems; I think it was the first time he tried it out on undergraduates. He was incredibly kind and patient; really interested to find out which parts of the explanation didn't work, and how he could get it across better.
