A split second after the knife descended, I realised I was in the presence of a manky onion. You know the ones I mean, where the knife squashes rather than penetrates, where there's a whiff of vinegar, and where some of the layers have turned translucent. If you're feeling thrifty, you can chop out the good layers and save the rest, but today, said onion was rapidly filed under B (for Bin). If I'd spent more time in the shop squeezing my onions (settle...), maybe I'd not be in such a situation, but I didn't so I was.
And the same is true with wine. Manky onions abound in wine shops and on restaurant lists. Bottles that have been badly stored. Vintages that should have been pensioned off. Wines that quite simply were bad in the first place. And - it's true - bottles that were simply having bad hair days. There's nothing you can do about the last situation. Even Jimi Hendrix went out of tune from time to time. But for the others, you're going to have to rely on experience. The more you taste, the more you should be able to tust your own tastebuds to know what's good and what's not. If you find themes emerging, then vote with your feet - or should that be with your Lafite?