Reuters: Four environmental campaigners breached security at London’s Heathrow airport on Monday, climbing aboard a parked aircraft and unfurling a banner protesting against runway expansion plans. Police later arrested the four from Greenpeace who walked through security at one of the world’s most policed airports. “Climate emergency. No 3rd runway” read the banner they hung on the tailfin of a passenger plane that had just landed after a domestic flight from the northern …