Trouble the government have is that they specified the need for one runway in the south east.
They have hitched their "one runway" waggon to LHR which their own figures now show to be the weaker case compared to LGW.If they press on and "decide" to approve LHR (is the weaker case) the government would be exposed to a Judicial Review which, if successful, would mean they have to start the process again from scratch.