Have you guys never watched "Yes Minister"?
David Cameron has said publicly that there won't be a 3rd runway at Heathrow. That was good for votes, but he really knows that a 3rd runway is the only short term option that makes sense.
So what does he do? He does what any government does...hold an inquiry! The outcome of said inquiry can almost be written now...Thames Estuary airport would be vastly expensive, heavily impact on the environment, would cause massive demographic shifts in the South East, leave the Heathrow corridor a ghost town etc. etc.
Dave now has an independant voice saying that Thames Estuary is not viable...and that Heathrow R3 is the only realistic option (with STN R2 maybe in the longer term). Dave then says that, reluctantly, he accepts that the new runway must go ahead, despite his concerns for the residents around Heathrow...the decision wasn't his, but the view of "independant experts".
We all get a new runway (and a little breathing space) at Heathrow, and Thames Estuary gets canned for another thirty years.
Simples!!
Am I being too cynical?