Mark became Director General of the Institute of Economic Affairs in December 2009. The IEA exists to further public understanding of the role free markets play in solving social and economic problems. The Institute pursues its mission through an extensive series of events and publications, outreach to students and teachers and articulating its case in the media. He has previously been Comms Director of Progressive Vision (2007-2009), Head of Media for the Liberal Democrats (2004-2007), National co-ordinator of NO2ID (2004) and Campaigns Director of Liberty (2001-2004).

In 2008, he co-founded the Orange Book ginger group, Liberal Vision.

He resigned his membership of the Liberal Democrats in 2009 to take up his new role at the IEA.

Mark is a regular commentator on radio and television on the state of the economy, the politics of the Coalition government and civil liberties.