Guardian: Boris Johnson’s plans to build a new airport in the Thames estuary could weaken a legal challenge against expansion of Heathrow he is helping to fund, it was claimed today. Stephen Knight, a representative from the 2M coalition of 22 local authorities opposed to a third runway at Heathrow, said a legal challenge based on the detrimental environmental impact could be undermined moves to increase flight capacity elsewhere in the south-east. Johnson has already pledged £15,000 of …