David Cameron and I visited the Open University the other day, he to give a speech to the world, me to learn something about day-old chicks and biochemistry. Neither of us knew the other was going to be there. I was told at the reception desk to wait on one of the seats behind me and handed a label, one of those clip things I can never work out how to fix to myself. As I turned to go to the chairs, preoccupied with my label dyspraxia, someone grabbed me by my elbow and pulled me to the left. I dislike being grabbed so I pulled away and carried on the way I was going. But I'd failed to notice that the world had changed while I had my back to the room, and a semicircle of large chests in suits were claiming all the space for the man at their centre.