Sudan began exporting oil in 1999

Now - stripped of its red carpet - it was being used to sneak illegally into southern Sudan, carrying humanitarian aid to rebel-held territory.

I lay back on the food sacks and hoped no government jets were prowling the area. We would have been hard to miss.

Two hours later we landed on a few hundred yards of flattish dirt outside what my map told me was a town called Wunrok.

I clambered out gingerly, like someone waiting to be mugged, bracing myself for the blast of hot air.

It never came. The year's first rains had arrived some hours earlier, cooling the air.

Instead I looked around and realised I was standing in one of those display cases from a natural history museum, the one labelled Stone Age.

It is an 18-year-old conflict that has probably killed more than two million people

It was late afternoon - sunny but quite mild. The countryside - all yellow and green - was dotted with beautifully thatched mud huts.

Four elderly men were walking through waist-high grass, carrying long wooden spears on their shoulders.

A group of naked boys were crouching by a tree near the river, sorting through a pile of tiny silver fish - their nets hung out to dry on the grass. Their boat was two hollowed out palm trees roped together, with the joint sealed with mud.

Modern war

And that was it. No cars, no signs, no metal, no coke bottles, no road to speak of, no trace whatsoever, of the modern world.

Well, that was my first impression anyway. It was wrong.

People here live in a state of permanent red alert

The next morning I was roused from my mud hut by the sound of a large airplane flying overhead. I rushed out and asked a local man called James Deng what it was. A government bomber, he said. He told me they flew over every day and could even show me the craters if I wanted.

"Round here there are two types of plane," he said. "The ones that bring food, and the ones that drop bombs."

So much for the rural idyll.

In fact Wunrok is trapped in the middle of a very modern civil war. One of the world's longest and most violent.

It is an 18-year-old conflict that has probably killed more than two million people. Every family in southern Sudan bears the scars.

One minute James Deng was talking quietly about this year's harvest - the next minute he was describing how, as a five-year-old he had run off into the bush alone at night to escape the slave raiders. He walked for three months, with other lost children, all the way to a refugee camp in Ethiopia.

Danger signals

The raiders (actually pro-government militias) still plague the region - charging in on horseback just before dawn armed with kalashnikovs, killing the men, stealing the women and children.

People here live in a state of permanent red alert - poised to run off into the bush at the sound of horses hooves or the drone of a plane.

A few hours later I was sitting under a tree talking to a man who suddenly revealed he had been attacked by a helicopter gunship the week before. John Wijial used his walking stick to imitate the rockets being fired at his house, killing two of his children.

The government, he explained, had found oil in the ground beneath his village.

"They want the oil," he said. "But they don't want us."

He hitched up his tattered clothes to show me where the shrapnel had cut into his thigh. He limped through the bush for five days to bring his family to safety.

Scorched earth policy

Oil has been discovered right across southern Sudan - like the war itself it is something the local population has no particular need for or interest in. But as always they are the ones who are paying the price.

Government forces have launched a scorched earth policy to drive civilians, and the rebels who live among them, out of the oil fields. That is where the helicopter gunships have come in handy.

Needless to say, international companies have been queuing up for a slice of the action - that includes British companies like Rolls Royce, which has provided engines to push the oil along the pipelines.

The nearest frontlines are about 50km (32 miles) from Wunrok. But the planes come an awful lot closer. Their bombs are often nothing more than old oil barrels filled with nails, pushed out of the back door.

Three days after I flew out of Wunrok, a cluster of bombs landed maybe 100 yards from where I had slept. This time, no one was hurt.