In the rugged plains of southern Sudan, Africa's longest war dashed the simplest hopes of two generations.

Yet the signing of a peace agreement between Sudan's regime and southern rebels has, at last, cleared the way for one of the most ambitious reconstruction and development schemes in recent history.

Only one Sudanese child in five goes to primary school
Last month, international donors meeting in Oslo pledged £2.4 billion for southern Sudan, including £300 million of British aid.

The task they have shouldered is monumental. This vast area has known only 10 years of peace since 1955.

The last round of a brutal conflict between the Arab-dominated regime and black African rebels cost two million lives.

Today, nowhere in the world compares with southern Sudan for poverty and backwardness. An area more than twice the size of Britain possesses hardly a single mile of tarred road.

Only one child in five goes to primary school and barely one in 50 finishes. Last year, only 2,000 boys and 500 girls completed primary school - in a region with 7.5 million people. The consequence is that three-quarters of adults are illiterate.

Worse, almost 70 per cent of infants are malnourished. One child in four will not live to see a fifth birthday. One child in five suffers from wasting illnesses caused by malnutrition. This toll of human misery weighs on the minds of aid workers. Salma Yousif is an assistant project officer for Unicef in Juba, the largest town in the south.

"The human cost here has been so high. You should not call it reconstruction because there is so little here. There is nothing to rebuild, nothing here to begin with."

Unicef distributes pencils and exercise books to Juba's 120 threadbare schools, 85 of which have no buildings and hold classes under trees or in mud shelters.

Donors plan to build new schools and restore existing ones, but there are no local contractors capable of doing the job, nor any supplies of building material.

Juba still suffers from the effects of war. It was the only large town in southern Sudan that remained under government control throughout the fighting. Rebels from the Sudan People's Liberation Army (SPLA) surrounded Juba and besieged its 250,000 inhabitants for 20 years.

Even today, it remains an isolated enclave. Landmines block every dirt road in the surrounding bush and it is supplied by aircraft from Khartoum, 800 miles to the north. Everything in the shops comes from the capital, meaning that basic essentials are two or three times more expensive than anywhere else in Sudan.

At local level, power-sharing administrations from the SPLA and the Khartoum regime will run Juba and the entire south. No one knows how this will work.

Foreign officials privately say that both sides are "in denial" about their new responsibilities and are waiting for others, notably the United Nations, to come up with workable arrangements.

Until this is resolved, southern Sudan will be incapable of absorbing the huge sums promised by donors.

So far, the reconstruction effort has hardly begun. "Forget about building roads now, it's a waste of time," said Andrew Robertson, a regional administrator for the UN's mission in Sudan.

Seasonal rains are about to begin, rendering road-building impossible until late October. "The planning should begin now, it should start today, if things are going to happen in 2006.

"These billions that have been promised, we've seen it time and again. The money's pledged and if it's not used, it's gone, finished, not available any more," he said.

Southern Sudan has some of Africa's best agricultural land and, if the fields were cleared of mines and connected by road or rail with the outside world, it could export its way to prosperity.