More gems from the Independent's scoop:
"Environmental and noise requirements: any new site will need to have a 16km long x 3.5km wide glide path either side of the airport, without overflying large built-up areas".
So no end of choices within half an hour W/NW of London, then. 
"It is unclear if Heathrow would survive should the plans be accepted, though it is thought the two could complement each other in the first years of the new airport's operations."
"What this idea does is put people's pipedreams, like 'Boris Island', to one side and shifts the political debate away from Heathrow, to work on something that is based on properly grounded infrastructure requirements."
"A motion at the Liberal Democrats' annual conference in Brighton will "firmly" reject the Thames estuary airport, rule out new runways at Heathrow, Gatwick and Stansted, and propose better use of existing capacity. It also demands an "independent, evidence-based study to find a location for a hub airport or a suitable airport to expand into a hub for the long-term" which could clear the way for the consortium's proposal."
And my favourite:
"Unlike most other airports in Britain, Heathrow is almost at capacity already, with 70 million passengers arriving and departing in 2011. Every day 190,100 pass through on 1,250 flights, drinking 26,000 cups of tea."
Clearly something needs to be done urgently to get those tea consumption figures up.
IoS exclusive: Secret plan for four-runway airport west of Heathrow - News & Advice - Travel - The Independent