An unusual story hit the headlines recently: a 115-year-old bottle of champagne had been found in Torosay Castle on the Isle of Mull. What made this case newsworthy was that the distinctive yellow label on the bottle in question, an 1893 Veuve Clicquot, was in mint condition, thanks to the cool, dark interior of the wooden sideboard it had been locked in for the past century.

I mention this because a reader recently asked me for some advice about an old bottle of champagne he'd inherited. He had heard such bottles could fetch surprisingly large sums at auction and thought it would be best to seek a valuation before pulling the cork. But where would you go to sell such a wine?

There are a number of firms in the UK that specialise in wine trading. Perhaps the first stop for a valuation would be one of the London auction houses. Both Christie's (0207 839 9060, www.christies.com) and Sotheby's (0207 293 6423, www.sothebys.com) have well-respected wine departments that regularly hold sales at home and abroad. In Scotland, Bonhams (0131 225 2266, www.bonhams.com) has a wine and whisky department. Auction houses are particularly good if you have a small parcel of wine or odd bottle of very rare whisky, but it's worth bearing in mind they take commission on any sales.

If you're lucky enough to have three or four cases of top-quality wine, it may be worth getting in touch with one of the many London broking houses. Farr Vintners (0207 821 2000, www.farr vintners.com) will only buy the very best by the case. Corney & Barrow (0207 265 2400, www.corneyandbarrow. com) and Justerini & Brooks (0207 484 6400, www. justerinis.com) have broking departments which are interested in acquiring fine and rare wine.

The importance of storage and provenance should not be underestimated. Delicate wines such as champagne and whites from the Loire and Burgundy are not as robust as those from Bordeaux and the Rhône. Anyone thinking about buying your wine will want to know exactly how it has been kept. (I have heard horror stories of First Growth 1990 Bordeaux left sitting in containers in the searing heat of Singapore. By the time they finally arrived at the London broker's office, the wines were ruined.)

Similarly, if the label is tarnished, the buyer will want to know why. Most important of all is the level of the liquid inside it. If the bottle has lost a few inches of wine and is languishing around shoulder-level, it may be difficult to sell. If there is any sign of seepage, it will be virtually impossible.

For all these reasons, odd bottles can be tricky to sell. The Antique Wine Company (0207 359 1109, www.antique-wine.com) might be able to help, and often pays more than auction houses. But don't expect miracles. Just because a wine is old doesn't mean it is valuable.

Vintage is important, particularly if your wine is more than 20 years old. Bordeaux's 1978 Château Mouton-Rothschild is a case in point, presently selling for £483 a case at auction. A case of the 2000 vintage, in contrast, could fetch £5,000. Some champagne vintages from the early-1980s are now past their best and the price will reflect that.

With most bottles, unless the market value is astronomically high, it's probably always worth drinking it, preferably with friends.

Three to drink now

2005 Cordier Prestige, Bordeaux, France, £9.99

A hearty claret dominated by notes of cinnamon, black cherries and the faint sweetness of strawberry. On the palate, there is a little oak and a pleasant taste of black coffee and caramel.

2007 Cordier Prestige, Bordeaux, £9.99

A wonderful mix of sauvignon blanc and semillion picked from vines growing on clay and limestone. There is a rich character to this wine, yet the smoothness is beautifully poised with firm acidity. It's a winner with Thai food.

2007 San Angelo Pinot Grigio, Banfi, Montalcino, Italy, £9.99

I adore this wine. It may seem unusual to find pinot grigio amid Tuscany's lush, warm landscape, but Banfi has a small patch of vines 350m above sea level that works perfectly with this variety. It has a rich, voluptuous character, while retaining a spicy, lean finish.

Stockists: Morrison's, Majestic