Friends of the Earth said the Thames Estuary airport scheme was a "pie-in-the-sky plan" and that Mr Johnson should "stop pitching communities in west London against those in Essex and Kent and back transport solutions that don't wreck our planet".
Rodney Chambers, leader of Medway Council in Kent, said: "For five years now, Boris has failed to listen to the huge number of people who have said that placing an airport in North Kent, on or near the Thames Estuary, is a complete non-starter."
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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.