Before entering Parliament in 2005, David worked as a solicitor for the Enfield firm Shepherd Harris and Co, specialising in criminal law and was an advocate in police stations and Courts in Enfield, Haringey and Hertfordshire.

In 2005-7 David helped lead the Conservative Party's policy work on drugs and alcohol with the Centre for Social Justice. In 2007 David became Shadow Justice Minister.

In May 2010, David was made Parliamentary Private Secretary (PPS) to the Rt Hon Oliver Letwin MP, Minister of State for Government Policy. In September this year, David was made PPS to the Rt Hon Owen Paterson MP, Secretary of State for Environment, Food and Rural Affairs. David has however retained his advisory role to Oliver Letwin in regards to drug and alcohol policy.