I thought that we were assured this sort of contamination was impossible

The Telegraph report that

"An oilseed rape crop in Somerset is to be destroyed after an inspection by the Department for the Environment Food and Rural Affairs discovered the seeds were contaminated with genetically modified material"

I seem to remember this Labour government assuring the public that such contamination was impossible. So how did this happen? I doubt that there will be an independent inquiry and anyway "independent enquiries" called by this Labour government have tended to be anything but independent.