I've always been good with numbers. We did mental arithmetic at Prince Rock Junior School, and I always scored near the top. Totting up columns of four-and-tuppences and such like was never much of a challenge when I had to collect on my paper round of a Friday night, and my GCE 'O' Level mark in mathematics ('hard sums', as a friend used to call it) was one of my best results. So it strikes me as passing strange that even though I can still add up my expenses without benefit of a calculator, I can't remember my own phone number without some sort of memory aid. I can remember…