Spot on, Dave. A similar rule applies to tomatoes. You can't make a decent tomato sauce with rubbishy, chemical-golfball shop tomatoes. If the toms are a tad disappointing but not complete rubbish, a scant teaspoon of sugar works wonders. I'll use those little piccolo toms to make a sauce, otherwise I'll use tinned plum tomatoes as long as there's no added salt in them. And if you want to kill a tomato, keep it in the fridge. And there's good science behind that advice.