Security has been increased around a farm in Hertfordshire where Genetically Modified wheat is being grown.
Campaigners planning to protest about the potential dangers of the experimental crops are being kept away from the crop at the Rothamsted Research centre.
Anti GM group "Take the Flour Back" is worried about contamination to the surrounding area. Rothamsted Research says the possibility of contamination from pollen blown in the wind is small.
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"All it takes is for somebody to see me - and I could just die, just like that. I could want to go to the shop and not come home."
Before the killing, Peters searched the internet for "serial killers", "treatment of child killers in prison" and "premeditated murder".
Arriva Rail North, Greater Anglia and South Western Railway are all affected.