It is expected that the Government will formally grant permission for Heathrow to build a third runway mid-week this week.
The issue will be discussed at a Cabinet meeting on Tuesday morning, and if objections from some Ministers can be quashed, the official announcement is expected to be made on Thursday.
This move flies in the face of the efforts of the Mayor (who has pledged to lead the legal fight against any such expansion) and a cross-party group of MPs, who oppose a third runway on environmental and climate change concerns.
It is expected that the cross-party group of MPs will give backing this week to Boris Johnson's plans for an estuary airport, reports the Guardian, forming an All-Party Group to further promote the issue in parliament. This move will offer them a significant bully-pulpit in the coming debate.
Bosses and unions are, predictably, backing the expansion vocally. However, if the Government goes ahead and offers formal backing to the project this week, it is clear that a wide and vocal coalition will be formed (albeit with a number of different motivations) against the expansion.
Against the backdrop of all this, Arup has set up a development company to start work on a proposed Heathrow rail hub. The idea of a high-speed rail hub has been backed by Labour and Tory politicians alike.
Join us over the next couple of weeks to read the views of the MPs and AMs who will have a key role in any debate over Heathrow's future.