Most of us think of farming as a rural pastime. In fact, agriculture is Britain's largest industry and, in the last 30 years, has quietly undergone a revolution.

Our farms are now producing 50% more than they did before the war, with a third of the labour force. This staggering achievement is largely due to the scientists and technologists.

But some farmers are beginning to question the whole approach: they fear that the new chemical farming may ultimately be self-defeating, and there are already signs that they may be right.