We called the radio station as we went, whenever we passed a pay phone, to tell them that we knew we were now late for a live broadcast, and that we were, promise cross our sweaty hearts, walking as fast as we could.

I would try and say cheerful, optimistic things as we walked. Terry said nothing, in a way that made it very clear that anything I could say would probably just make things worse. I did not, ever, say, at any point on that walk, that all of this would have been avoided if we had just got the bookshop to call us a taxi. There are things you can never unsay, that you cannot say and still remain friends, and that would have been one of them.

We reached the radio station at the top of the hill, a very long way from anywhere, about forty minutes into our hour-long live interview. We arrived all sweaty and out of breath, and they were broadcasting the breaking news. A man had just started shooting people in a local McDonald’s, which is not the kind of thing you want to have as your lead-in when you are now meant to talk about a funny book you’ve written about the end of the world and how we’re all going to die.

The radio people were angry with us, too, and understandably so: it’s no fun having to improvise when your guests are late. I don’t think that our fifteen minutes on the air were very funny.

(I was later told that Terry and I had both been blacklisted by that San Franciscan radio station for several years, because leaving a show’s hosts to burble into the dead air for forty minutes is something the Powers of Radio do not easily forget or forgive.)

Still, by the top of the hour it was all over. We went back to our hotel, and this time we took a taxi. Terry was silently furious: with himself, mostly, I suspect, and with the world that had not told him that the distance from the bookshop to the radio station was much further than it had looked on our itinerary. He sat in the back of the cab beside me white with anger, a non-directional ball of fury. I said something hoping to placate him. Perhaps I said that ah well, it had all worked out in the end, and it hadn’t been the end of the world, and suggested it was time to not be angry anymore.

Terry looked at me. He said, “Do not underestimate this anger. This anger was the engine that powered Good Omens.”

I thought of the driven way that Terry wrote, and of the way that he drove the rest of us with him, and I knew that he was right.

There is a fury to Terry Pratchett’s writing. It’s the fury that was the engine that powered Discworld, and you will discover it here: it’s the anger at the headmaster who would decide that six-year-old Terry Pratchett would never be smart enough for the Eleven-Plus exam; anger at pompous critics, and at those who think that serious is the opposite of funny; anger at his early American publishers who could not bring his books out successfully.