Doreen McIntyre from campaign group 'Harefield Against HS2' spoke to our Political Correspondent Simon Harris and described how a new viaduct planned for the building of HS2 would change the face of the area.
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The victim ran along the platform with his friend when the attacker pulled out a knife and chased them both.
Spray cans were found near the bodies on tracks near a south London station.
Some 81% of passengers are satisfied with their journey, down three percentage points from spring 2017.