The tyre had gone a bit slick
That wasn't all. The bike came with cleat-compatible pedals. So I tend to bike with bike shoes. You can use normal shoes on them too but it's not very comfortable; you're resting your foot on too small a surface. And if I come with bike shoes into the office I just change into my office shoes. But sometimes I lecture in the morning and the afternoon! So then I lecture before I have had a chance of putting my office shoes on, and after I've already have taken them off. And I don't like the feeling of walking around on cleats. You hear and feel the metal scratch on the street. The worst is if I have to go to the shops too! Or if I walk on a wooden floor. So even though I appreciate cleats; it allows you to both push and pull. But I knew there were pedals that were cleat-compatible on one side and civilian shoes compatible on the other side. So I bought a pair! When I did, the bike shop people said I might find I would not be able to get the old ones off, and if that were the case, I should just bring the bike back in and they would help me. And lo and behold: I couldn't get the old ones off. So I brought the bike back in. And they sorted it!
New pedals in place!
So now I can bike around with or without cleats, in comfort! I like it! My commute has just got better.