How to test restaurant wine

One of the loveliest aspects of fine dining is the ritual of testing the wine before you and your dinner party companions drink it.

Not only is it good manners on the part of the restaurant, it can also, if you squint, make you feel like royalty. But what are we really doing when we "check the wine" and give that soft nod to the waiter? I mean, apart from feeling like the ruler of a small province. Sommelier Matt Skinner says we're searching - or sniffing, rather - for two things: cork taint and oxidation.

"At its most obvious, corked wine will have an unmistakable smell of wet cardboard and mould," says Skinner. "Smell it once and you'll never forget it. Oxidation, on the other hand, is the effect of excessive oxygen on wine. Unlike corked wine, it's possible to see the effects of oxidation - particularly on white wine, where the liquid will turn a deep gold, almost copper, colour, while red wine will generally begin to brown. The most obvious way to spot an oxidised wine is by smell: it will have lost all that lovely fruit character and you'll be left with a wine that resembles dry sherry or vinegar."

The general rule is that whoever orders the wine will be the person required to taste it when it's presented at the table. When you're presented with it, Skinner suggests that you only need smell it. "If you're unsure, by all means taste the wine," he says, "but it's not really necessary." If the wine's bad, speak up - but bear in mind that you can't return your wine simply because you don't like it.