Let's take a break from grape varieties – we will return to them next month. In this article we will have a look at a phenomenon in the wine world: en primeur.

 Each year the great châteaux of Bordeaux mount a sales campaign to sell the production of their most recent harvest. It is, in effect, a wine futures market: you pay for the wine before it's bottled in the hope that the wine will increase in value subsequently. This is the en primeur market. A few other wines are sold en primeur, but the important market is in the wines of Bordeaux.

 Bordeaux produces more wine than any other region on earth – it produces more wine than the whole of Australia, and the red wine from the region is known as claret. There are thousands of growers, estates and producers, and at the top are the great Classed Growths of the Medoc: 61 châteaux chosen by the Bordeaux wine brokers (on the basis of the prices their wines were fetching), divided into five sections – First to Fifth Growth – to represent the best of Bordeaux at the 1855 Exposition Universelle in Paris. This classification remains in place, with the exception that Château Mouton-Rothschild was promoted from Second to First Growth in 1973.

 There is currently a huge amount of publicity surrounding this year's en primeur campaign, with a lot of fuss being made in the press about the 2009 vintage, on the grounds that it is the vintage of the century. So is it worth buying en primeur?

Like the stock market or betting on the horses, it's a gamble, and the better informed and/or better advised you are, the more likely you are to do well out of it. But there are plenty of pitfalls: first, choose a reputable merchant that will still be in existence when it is time to take delivery of your wine – quite a number of people have had their fingers burnt by buying from dodgy traders who then disappeared or went bust; secondly, pick a vintage that is likely to be popular – let me explain the reasoning for this: if it loses popularity, you will be able to pick it up more cheaply later. And consider this: currently I have in my shop on the shelf Château Gruaud-Larose 2004 (a Second Growth) priced at £37.50 including VAT, duty and everything; the 2009 Gruaud-Larose has just been released, and I have been quoted euro 39.40, but this is before the costs of shipping from France, duty, VAT and delivery to the customer; nor can you open a bottle and drink it (which you can with the 2004, and very nice it is too, I had some a few days ago), you will have to wait at least another two years – and the final cost will work out at at nearly £50. While 2009 looks as if it will turn out exceptionally well, 2004 is an underrated vintage, and is giving great drinking pleasure, though it will give less pleasure to show-offs who wish to impress other people!