The rains have failed this year, and even when they come, the soil has been depleted of its nutrients through overuse. For far, far less than the cost of a nuclear bomb, we can save millions of people with vaccination programmes. There is no margin of income above survival that can be invested for the future. When people say Africa needs 'trade not aid', they miss the point. They need trade plus aid, or they will never get out of the poverty trap.

We have calculated you actually need a small amount to end all of them, just $15bn, a 30th of what the US spends on the military - and then you have trade."At its best, aid can provide what I call 'weapons of mass salvation'. But there is no time to make this observation: he is locked in Nthandire. "And the village was levelled by another disease that we could deal with easily: malaria," he says. "As many as three million people die in Africa every year of malaria."Even though it is a preventable disease if you use bed-nets and other environmental controls There is no clinic nearby to help with this There is no aid here. That's what my friend Bono calls insane, stupid poverty, deaths for the price of pennies, and it's true.The role of aid, Professor Sachs says, is to lift countries out of "poverty traps" like this. "When you are struggling to live from day to day, struggling to eat, you have no surplus capital to build roads or to acquire medicine or malaria nets, and nor does your government."So your poverty literally traps you. They used these plans and appealed to the international community for the means to treat a third of the total infected population - 300,000 people - with anti-Aids drugs."And you know what the international community said? The plans are 'too ambitious' Cut them.

So the government in Malawi cut their plans to saving 100,000 people Still it was too much. The international community told them to cut another 60 per cent from the plans In the end, only 25,000 people were saved That's not a failure of African government. That's a failure to give enough aid to a good African government."With his solid black hair and preppy smile, Professor Sachs looks like Barbie's ex-boyfriend, Ken, worn down by a life of seeing things a preppy boy just shouldn't see. They had structures for drug delivery, patient counselling, community outreach, everything. * The House of Commons contains its fair share of poison chalices, but the ambitious Labour MP Jim Knight has just been landed with what can comfortably be described as the worst job in Government.