Cost counts when it comes to caviar, says Annie Bell. Photograph by Patrice de Villiers
It can be very difficult when a food is expensive to divorce the taste of money from the taste of the article. Would we rave as passionately about turbot, black truffles and priceless drops of balsamic vinegar if they cost next to nothing? I suspect we'd celebrate our good fortune and eat a great deal of them, but without getting quite as excited about the prospect. There's no escaping the lure of the unavailable. And, unless you are seriously rich, there is little in the world of food less available than caviar.

Without wishing to sound princessy, I love caviar. I love all caviar, so long as it is pearly black, salty and dissolves with exquisite tenderness in the mouth. I do have minor preferences, and have never really questioned that most of all I love beluga, followed by oscietra, and finally, given no other choice, I'll settle for sevruga, I feel sure I am not alone in this preference, after all why should anyone question this pecking order when in theory you should get what you pay for?

So why is it that every caviar dealer I have ever talked to states a preference for sevruga? They are the ones, apart from the seriously rich and fishermen, who get to eat it day-in and day-out, and to compare sevruga with oscietra and beluga, royal with imperial, Russian with Iranian, which is what I have done on this rare occasion of being asked to write about it.

However, before the mother of pearl spoon can touch your lips there are the politics of the Middle East and the USSR to tackle. The complications wrought by the dissolution of the USSR have been phenomenal; there is no longer any central control. For the average man in Russia who sees a sturgeon sailing past, it represents one month's wages. And the fact they don't know how to process it properly doesn't prevent it from coming on to the market.

This has given rise to horrendous overfishing which has prompted CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) to issue a CITES Appendix II protection order for sturgeon that will come into place next 1 April. This is intended to wipe out large- scale trade in contraband caviar by forcing those importing and exporting it to trade with a licence.

One of the finest names in caviar in London is WG White, the oldest purveyors in London, who supply Harrods, Marco Pierre White, Fortnum and Mason and British Airways with probably the most expensive caviar in the country. Whereas 10 years ago they dealt mainly in Russian caviar, today they sell just 20 per cent Russian and the remaining 80 per cent is Iranian. But it hasn't proved such an unhappy transition: as far as Laura Morris- King of White's is concerned there is a distinct difference in quality between the two.

While Russian caviar is salted, Iranian is spiced up with salt and salt borax. This is normally used as an antiseptic cleaning agent, also in the making of glass and china and was illegal in this country until a few years ago, it is also what gives caviar its finest flavour. I won't get into a debate about the health implications, I don't say the salt would kill you long before the borax if you ate enough of it. Caviar needs salt and it welcomes salt borax: at the time that the roe are harvested from the sturgeon's belly they taste, as Laura Morris-King puts it, "like soapy dishwater".

There is also a difference in eating terms depending on where the sturgeon are netted. In Russia, the fish are caught in the river when they are ready to spawn and the eggs are soft, whereas in Iran they are caught in the sea and the eggs are that much firmer. If you need any persuading about the difference then you should try the sevruga - you'll find the Russian has a distinct flavour of fish oil by comparison to Iranian.

Laura Morris-King did a good job of convincing me of the merits of Iranian caviar. All that was left was to decide which kind was preferable. And for this I tasted them blind, concealing the colour-coded lids of the thing to avoid the prejudice that would come of knowing that beluga, the rarest of all that represents just 2 per cent of the catch, is that much better than sevruga on account of its price. In fact the size and colour of the eggs was something of a giveaway, but with enough concentrated tasting the conclusion of the tasters was unanimous.

Beluga is fabulous. It sells itself on consistency with its large and voluptuous eggs that separate out on your tongue, they are creamy with a hint of walnut and literally melt. Then there is oscietra, often described as being mellow and milder than the beluga, although this can vary considerably, occasionally tending to bitterness. When it came to flavour it was the small and salty eggs of the sevruga that stole the day. These possess far and away the greatest depth of flavour with a real pungency of the sea. None of the others compared in terms of flavour. Basically, if you are buying beluga then you are buying texture.

Only once have I ever experienced eating too much caviar. Like a cokehead's dream of an urn filled with white powder, there was a large tureen placed centrally in the middle of the room and the spoon provided for serving was not a teaspoon but more the size of a tablespoon. At the time, it was bliss, but the after - effect was a thirst that lasted all day and into the night, added to which it is incredibly filling.

Laura Morris-King recalls the time she went fishing for sturgeon on a Russian vessel. Supper was a very basic fish soup, with (and I've double-checked this figure) one pound of caviar stirred into each bowl of soup, washed down with vodka. However, the second or third day she said the novelty palled, which just goes to show.

Last year, the price of sevruga went up 40 per cent, and there's no telling what will happen now that oil's been discovered in the Caspian Sea. Just think how good it'll taste if the price goes up even further

WG White: telephone 0181-831 1400 for mail order

For the average man in Russia who sees a sturgeon sailing past, it represents one month's wages