KA and I shared delivery of the lecture. Somehow I ended up with the ‘hard’ bit: explaining the difference between linear and complex computer programming.

My instructions said to use railway tracks as an analogy, and make reference to a bacon, egg and mayonnaise roll. This made no sense to me whatsoever.

I knew that one of the boys in the class was from Stockton-on-Tees. He was bound to know about trains, and could help me with the analogy. I could barely conceal my disappointment when it became obvious that Robbie had no idea of the part that his home town had played in the world history of the railway.