Entering the door are former ministers, MPs, senior advisers and public servants with years of experience behind them on the intestine-like inner workings of governments, politics and policy making.
As they exit the door, many become part of the opaque and mostly unreported world of corporate and industry lobbying.
Treasurer Wayne Swan has publicly questioned the power and influence wielded by vested interests in the mining and resources industries.
In his recent essay for The Monthly, Mr Swan chose to name three people in particular – Gina Rinehart, Clive Palmer and Andrew Forest – as representing this undue power which is shaping public policy for the narrowest of interests.
Vested interests had worked together to undermine climate policy and mining taxation, he wrote. Australia’s success was in “jeopardy”, vested interests were a “poison” threatening the future prosperity of the “great mass of good hearted Australians”.
Mr Swan picked on a small number of super-rich mining magnates, leaving multi-billion dollar corporations and industries that work equally as hard for their own interests wondering what they’d done to escape the Treasurer’s wrath.
The essay was brave and most likely, in my view, broadly accurate. But it was heavy on the rhetoric and light on solutions.
Mr Swan could have taken the opportunity to call for more transparency and openness in the systems that regulate lobbying and political donations.
He could have supported the calls in the just-closed Senate inquiry into lobbying for stronger oversight of lobbyists.
He did neither.
Yet it is the same industries that Mr Swan is criticising – fossil fuels and resource extraction – that can afford to scoop up the talent from the public service and put them to work in a system that allows them to operate largely unseen.