It was 7.30 in the morning last week when 35 masked raiders broke down the gates of the Federal Institute of Technology’s agricultural centre near Zurich. Within minutes they had trampled to the ground the carefully planted testbeds of genetic­ally modified wheat, rendering useless a scientifically controlled experiment to assess the value – or danger – of GM seeds.

An ocean away in the US, farmers are already contemplating this year’s soyabean and maize crops. Rather than being concerned, as in Switzerland, where the government recently extended a GM moratorium for three more years, growers in the vast prairies of the Midwest have so warmed to GM seeds that they now account for almost the entire maize and soya output of the world’s biggest ­producer.