The Labour government approved a third runway for Heathrow in 2009, in the face of loud opposition from locals.
Cameron cancelled the project when he formed a coalition government following the 2010 election.
Labour's new leader, Ed Miliband, has reversed his party's support for a third runway as well.
A study published by the British Chambers of Commerce earlier this year claimed that a third runway would add 30 billion pounds ($48 billion) a year to the U.K. economy, and that every year of delay cost the nation about 1 billion pounds ($1.6 billion).
I just thought readers of my diary should be aware of this!