In 1970 Dr Norman Borlaug was awarded the Nobel Peace Prize for advances in agricultural technology which had produced new 'miracle' rice and wheat. The 'Green Revolution had arrived; it was hoped that world hunger would disappear.

But in the years which followed the new technology only seemed to make the rich farmers richer and the poor farmers poorer. How have agricultural scientists responded to this?

Through the eyes of an economist, Keith Griffin (President of Magdalen College, Oxford) "Horizon" looks critically at the new 'Green Revolution' as scientists work in Mexico, Bangladesh and the Philippines to help the poor grow more food.

Their new approach may offer some hope - but unless there are equal changes in economic and political structures are other kinds of revolution inevitable?