Stephen Sackur talks to Mark Lynas, a veteran green activist who once led a campaign to vandalise experimental genetically modified crops. But that was then - now he says that GM technology is entirely safe, and is a necessity if we are to feed the planet. He has made a similar U-turn on nuclear power too.

The zeal of the convert can be a factor not just in religion but also in scientific debate. He says that he has junked ideology in favour of hard science. But is it really as simple as that? Show less