I was looking at ageing in action, in black-and-white MRI pixels, death and dissolution foretold, and already partly achieved. My 70-year-old brain was shrunken and withered, a worn and sad version of what it once must have been. There were also ominous white spots in the white matter, signs of ischaemic damage, small-vessel disease, known in the trade as white matter hyperintensities – there are various names for them. They looked like some evil pox. Not to put too fine a point on it, my brain is starting to rot. I am starting to rot. It is the writing on the wall, a deadline.