Charles Avaala was standing beside the main road to Bolga Tanga in northern Ghana when I first met him. He had a crate of tomatoes at his feet and was waiting for buyers to come from Kumasi, Ghana's second city, or Accra, its capital. It was midday and the temperature was almost 40C. Charles's tomatoes, and Charles himself, were beginning to look rather weary.
He explained that he once grew his tomatoes exclusively for the Pwalug cannery, which closed in 1989. I had already met a former commercial manager of the plant, George Jato, who had been reduced to acting as its caretaker, watching over dormant machines.
Since the closure Charles had been forced to sell his produce by the side of the road. "Sometimes traders come and sometimes they don't," he shrugged. "And then the tomatoes go to waste."
Asugre Akasoa was standing a few feet away with an equally voluminous crate full of ripe tomatoes. "I used to work in the cannery," she told me. "When it closed I lost my job and now I'm a market trader trying to sell the tomatoes I once put through the machines."
The state-owned cannery was closed at the behest of the World Bank and the International Monetary Fund as part of an ongoing programme of economic changes, known as "structural adjustment", designed to cut government expenditure in Ghana and open up state industries to private enterprise. A buyer was never found. So Charles and Asugre, and hundreds of other people in the surrounding area, lost their main customer and employer.
Ghana also made promises under the same programme to open up its markets to competition from abroad. So, as tins of Ghanaian tomatoes were disappearing from the shelves of the country's shops, Italian tomatoes wererapidly filling the space. With import tariffs reduced, the heavily subsidised Italian tomatoes were cheap. By 2001, Ghana and its west African neighbours were importing 64,900 tonnes of tinned tomatoes and tomato paste.
"Everyone's eating the Italian tomatoes now," George Jato had told me. "It's heartbreaking to see how we've lost our own market."
Even more heartbreaking is the fact that the European Union pays out subsidies of around £250m per year to support its tomato farmers, while Charles and his compatriots are not allowed to receive any support from their own government. To this day, the World Bank and IMF are instructing Ghana to cut back its expenditure.
In Britain few people pass through Tesco or Sainsbury's without buying tins of inexplicably cheap tomatoes from Italy. In a fairer world you and I would also have the opportunity to buy tins full of Charles's tomatoes. But as consumers, we are seldom offered these kinds of choices.
Such is the world of trade - favourable to those who can afford to take advantage of it, and beyond the reach of those who cannot. This weekend, in the Mexican beach resort of Cancun, 146 trade ministers from the member nations of the World Trade Organisation are continuing to apply their collective negotiating power to this inequitable equation.
Britain's position in the mighty conundrum has traditionally seemed duplicitous. The Government claims it wants to make trade work for poor people, but government ministers are also powerful advocates of free trade - the same free trade that is killing many vulnerable industries, such as tomato-growing in Ghana, and putting some of the world's poorest people out of business.
Patricia Hewitt, the Secretary of State for Trade and Industry who is leading the British delegation to the WTO, argues for trade that is "free and fair". But on the way to Cancun she accepted an invitation from Christian Aid to meet poor producers in Honduras. Last Thursday, under angry skies that often let fall raindrops the size of marbles, she met rice farmers, all of whom had been badly hit, and some put out of business, by cheap rice imported from the USA.
Escaping the rain, the minister found herself squeezed on to the tiny veranda of Maria Marcos Rivera, a 62-year-old rice farmer who is now no longer producing. She told Hewitt how the rice she grew could not compete with the rice from America, where farmers receive huge subsidies and where, having benefited from decades of protection, they have highly efficient and mechanised farms. Not growing rice has crippled Maria's ability to provide for the five generations of her family that live in the house. "I have had to cut back on lots of things and can now really only afford to buy the barest of essentials, such as maize and beans and soap," she said. "I cannot even afford to buy clothes now."
Maria's good humour and courtesy towards the Secretary of State partially masked the deep tragedy that she and millions like her across the developing world are living through. It is a tragedy shared by Charles Avaala in Ghana, onion farmers in Senegal and oil seed producers in India - all of whom are sinking because of a global trading system that is failing the poor.
To her credit, the minister seemed to be hearing what Maria Marcos Rivera and the other rice farmers whom she met that day had to say. The government of Honduras has recently recognised that its rice industry is heading for disaster if forced to slug it out in the market place with imports. It has drawn up a new agreement that obliges millers who wish to import to buy Honduran rice first. Ms Hewitt left Mrs Rivera's farm agreeing that this kind of protection is necessary in the short term for small-scale producers in poor communities. It sounded like quite a turn around from the usual mantra that free trade is the best way to boost incomes for most people in the world. But the minister also maintained that there does not seem to be a longer-term future for Maria and those like her that would see them continue as owners of small plots of land, growing crops for cash. She dismissed the plight of such small-scale producers as "condemning people to that kind of poverty". Only larger tracts of land owned by bigger concerns can make agriculture economically viable, she maintains.
This will come as heartbreaking news to Maria, since 20 years ago she had to struggle, along with a group of other people, to first seize, then occupy and eventually own the land she now longs to farm again. She was a day labourer on other people's farms before then. It seems that in Britain's vision of a world where trade works for the poor, she would be a day labourer once again.
The relationship between poor people and their land should not be romanticised. Christian Aid's experience of small-scale farming, gained through working in communities where the majority of people are smallholders, is that it is a tough, often unrewarding life. But there is one question that remains unanswered by advocates of free trade for poor countries. If Maria Marcos Rivera does not grow rice and Charles Avaala does not grow tomatoes, then what exactly are they supposed to do to support themselves and their families?
Do they join the millions who are flocking to rapidly expanding Third World cities where there is every chance they will end up living in miserable slums rife with drugs, prostitution and HIV/AIDS? Or do they look further afield and attempt the hazardous trek to join the queue of economic migrants seeking a better life in rich countries? Maria's brother tried to get to the USA to try to build a better life. But he only got as far as Mexico before being deported back to Honduras.
And what would be the consequences for Honduras, a country where more than 60 per cent of the population still lives and works in the countryside, or for Ghana, where nine out of every ten people living in the north of the country are poor? In both cases, many of those at the sharp end are small-scale farmers. Are they all to become illegal migrants to the USA or Europe, sending money home to their families?
Deep down most of us realise we cannot sustain a world where almost half the population lives in poverty, and where stable, comfortable lives in the West are in such stark contrast to those of poor people - blown in ever decreasing circles, like chaff in the wind, by the policies we shape and influence.
Yet this weekend in Mexico the rich countries are once again leaning on poor countries to open up their markets further, while stalwartly holding out against lowering their own levels of subsidy or their tariff barriers to level the playing field in a meaningful way.
Before countries like Honduras and Ghana can be expected to compete in even this fairer kind of world, they must be allowed to shore up and protect their own producers, to begin to repair the damage that has already been done to their economies by "one size fits all" liberalisation. They need unfair trade with the rules canted in their favour for a change.
The noises that Patricia Hewitt is now making do sound encouraging. But the moves of our government and those of other rich countries must be watched carefully over the coming days and months. We need firm evidence that these are not just soothing words.
The next time you are in the supermarket, try looking for a can of Ghanaian tomatoes and think of Charles Avaala and those like him. How can any rich government maintain that free trade has given these poor people a fair deal?
Andrew Pendleton is trade policy officer for Christian Aid
So what was cooking?
A recipe for disaster, according to Christian Aid. First prepare your ingredients in rich countries, with subsidies. Crack open the markets of poor countries using the clout of international organisations so that little or no duty is paid. Tenderise those markets by preventing governments from giving cheap credit or advice to their own farmers. Then:
Smear the paste over West Africa until locally grown tomatoes go rotten. Canneries and farms lie dormant in Ghana as it imports 69,400 tonnes of cheap European paste instead.
Pour American rice liberally on Honduras until farmers go out of business. Most have no other source of income. Honduras imported 222,560 tonnes in 2001 as its own production fell to an all-time low.
Fry the livelihoods of Indian soya-bean farmers in the oil. India was the fifth largest producer of soya until the WTO forced it to lift restrictions on imports, which increased 60 times over. Now India sells half what it used to.
Dice the Senegalese market by sending 52,041 tonnes of Dutch onions during the year. Dump poor quality stuff there - local farmers do not have the technology to store their crops, so they are helpless.
Chop up the chicken and ship it to Ghana to be sold more cheaply than home-grown birds. Farmers and grain producers struggle under the weight of 23,105 tonnes imported from Europe and US.