05/09/2012 05:40 BST | Updated 04/11/2012 05:12 GMT

Greening Departure Reignites South East Aviation Debate

In one of the most controversial moves of his first reshuffle David Cameron pushed Justine Greening out of her job as transport secretary and brought in chief whip Patrick McLoughlin.

The decision came after Greening re-affirmed her opposition to a third runway at Heathrow following Tim Yeo's call for a change of policy last week.

There are clear reasons why the government might want to change its policy on Heathrow. The economy remains in recession and there no sign of imminent recovery. The government desperately needs to be seen to taking action to improve competitiveness and aid recovery. Moves to increase air capacity in the south east would please business groups, who have long been eager for expansion, and want to see London retain a hub airport.

The need for a hub is a crucial part of the debate. Heathrow currently provides the majority of the UK's long haul flights but is operating at 98% capacity. Gatwick and Stansted could still expand but that would not necessarily stop London from being overtaken by Paris and Amsterdam as a European hub.

Expensive solutions such as building an airport in the Thames Estuary have been flouted. Boris Johnson is known to support this option. But such a project would be prohibatively expensive. One design proposed by architect Norman Foster would cost around £50 billion. Five times more than it cost Britain to host the Olympics!

Building a new runway at Heathrow, although unpopular among West Londoners, would be a vastly cheaper way of solving this problem. And by bringing in Patrick McLoughlin David Cameron may be laying the groundwork to make this decision.

It would always be difficult for Greening, MP for Putney in West London, to countenance expansion at Heathrow. McLoughlin as MP for Stafford has less baggage in this area. He has also shown signs of supporting expansion at Heathrow in the past. Whilst Minister for Aviation and Shipping in the early 1990's he refused to rule out expansion at Heathrow.

Boris Johnson has already reacted to McLoughlin's appointment. He argued that it showed the government intends renege on its promises over Heathrow and restated his personal opposition.

Though not everyone is so sure that Greening's departure means that an estuary airport is on the back burner. James Forsyth, Political Editor of the Spectator, suggested on twitter that Greening was moved out because lots of Kent MP's do not want an estuary airport, and it is hard for her to tell them to accept it.

Despite it's enormous cost there are good reasons to build an airport in the Thames Estuary. There would be less air and noise pollution for London residents. It would aid the continuing redevelopment of East London which would gain exceptional links to the world. And it would provide massive investment at a time when the country is languishing in recession. Investment that would not only boost the economy, but leave the country with a world class air hub at the end of it.

So perhaps David Cameron is playing a clever game by bringing in a Transport minister that allows all options to be considered.

Any U-turn on Heathrow is unlikely to come soon, the coalition agreement rules it out. Nonetheless is clear that the South East's aviation debate is back on the agenda. And in Greening, it's already claimed it's first political casualty.