The film lays much of the blame for this with the New York Trading market, a "destructive mechanism" for the coffee producers, since the market price of coffee is sometimes now set below the amount it cost to produce. The world economy in coffee is controlled by four big multinationals - Kraft, Nestl‰, Procter & Gamble and Sara Lee - who are largely able to determine the price of coffee to their own advantage. The farmers - most of whom have tiny family farms - cannot sell direct to this market, but must go through middlemen - exporters who themselves take another sizeable chunk.

This is where Fairtrade comes in. By paying the farmers a guaranteed price set above the fluctuating values of the international commodities exchange, the Fairtrade system can slowly pump modest quantities of money back into the farming communities, allowing them to build such "luxuries" as schools, health centres and clean-water pipes. The hero of Black Gold is Tadesse Meskela, an amiable man, the General Manager of the Oromia Coffee Farmers Cooperative Union. Meskela's job is to fly round the world securing better prices for the

74,000 Ethiopian farmers he represents. Non-Fairtrade coffee reaches the consumer after six chains, each of which reduces the chances of the farmer getting a reasonable price. Working through cooperatives can reduce the chains by 60 per cent.

For two-and-a-half years, the film-makers followed Meskela on his journeys.

"Our hope is that one day the consumers will understand what they are drinking", he says, but not much that he sees indicates that they will.

We share Meskela's bafflement and distress at how hard it is to make Ethiopian coffee pay, despite the fact that Ethiopia is the birthplace of coffee, and still regarded by gourmets as producing some of the world's best beans. Meskela is shown in a branch of Waitrose in London, in the coffee aisle, staring miserably at all the choice. Many of us have stood in just such a pose, vacantly pondering which of the many prettily designed packets we will take home and decant into our cafetiˆres. Meskela's problem is different. He observes the consumers with their baskets, and sees how few of them bother to buy Fairtrade coffee. Then he finds some Fairtrade coffee on the shelves - but it comes from Latin America, not Africa. Finally, he rummages, and finds a tin of Mocha Sidamo coffee hidden away where no one would see it.

Many of the farmers he represents are now switching from coffee crops to chat, a narcotic plant which is banned in the United States and much of Europe.

Several bemused Ethiopian farmers are interviewed about it. They don't like chat, they say. They know that the people who chew it are addicts. But they need cash, and chat pays far better than coffee. What can they do? The economics of coffee simply make no sense for them. The concluding section of the film shows footage from the 2003 trade talks of the WTO in Canc”n, Mexico, which collapsed, amid protests from Third World countries about the refusal of the US and European Union to drop subsidies for their own farmers, when Africa was forced by the IMF to drop its own subsidies. In this context, it is virtually impossible for African trade to compete. If Africa could increase its share of world trade by just 1 per cent, it could generate $70 billion - five times more than the entire continent now receives in aid. There are no signs of this happening, however. The Ethiopian coffee farmers continue to go hungry; and we continue to line our bellies with endless milky lattes. If we should have a moment's worry about the ethics of what we are drinking, we can appease it with the bromides which issue from the Starbucks information machine. The perky manageress of the original Seattle branch tells the camera that coffee is not the main business of Starbucks, anyway. "We're in the people business, selling coffee", she exclaims, before going off to sell another giant mug of foam.

The makers of Black Gold seek to depict the mindless coffee-drinking of the West as a fundamentally anti-democratic activity. The twenty-first-century coffee house has become the symbol of selfish, solipsistic, blinkered consumerism. We are a long way from the coffee culture of the eighteenth century, which, we are supposed to believe, was a model for benign democratic activity. By 1750, there were probably more than 2,000 coffee houses in London, places where men went to read newspapers, smoke tobacco, conduct business, see friends and drink a murky brown liquid which went under the name of coffee. Now that cultural history of the eighteenth century is dominated by the influence of J’rgen Habermas, the institution of the coffee house is generally treated as a prime example of the "public sphere" in action, what Habermas called "a realm of our social life in which something approaching public opinion can be formed".