Flabby, vaguely disorientated and, more than three years on, still struggling with stroke recovery, I am on a radical diet. No booze, no caffeine of any kind, no lots of other things — sausages, bacon, roast meat, you name it. Not a lot of fun, but the revelation has been coffee: for well over 40 years I have believed that I can only function in the morning after pints of coal-black, extremely strong caffeine.