Jon Griffin from the Enviroment Agency said: "This site has an absolute limit of 5,000 tonnes of waste at any one time allowed to be stored in there. They've gone way over that for quite some time.
"We've told them to clear the site basically if all the waste and that is the only way to stop the fires that keep breaking out and causing misery for the local residents. This is the worst site I've seen in my career"
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Paramedics were on standby outside the police cordon as armed officers stood by the property.
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The action comes on top of an emergency timetable which has seen hundreds of trains a day being axed.