He is a Second Permanent Secretary at Her Majesty Treasury. At the Treasury, Kingman was closely involved with the response to the financial crisis in the United Kingdom. In 2007-2008 he led the response to the collapse of Northern Rock, and in October 2008 he led negotiations with RBS, Lloyds Banking Group and HBOS on their recapitalisation by the United Kingdom Government. In November 2008 he was appointed as the first chief executive of United Kingdom Financial Investments Limited, the company created by the United Kingdom Government to manage the banking holdings acquired during the crisis.
From 2010-2012 Kingman worked at Rothschild & Company, the investment bank, where he was Global co-head of the Financial Institutions Group.
Previous roles in the Treasury have included Press Secretary to the Chancellor of the Exchequer, Director of the Enterprise and Growth Unit and Managing Director responsible for public spending control. In 2004 Kingman led a cross-Government 10-year review of United Kingdom science funding.
As of 2015, Kingman was paid a salary of between £160,000 and £164,999 by the department, making him one of the 328 most highly paid people in the British public sector at that time.