Dr Middlebrook has published widely on the challenges of economic development and post conflict reconstruction, with much of his work focusing on public and private investment, restructuring of government institutions, political analysis and the political economy of economic growth and poverty reduction.

He is the Joint managing director of Middlebrook & Miller, a private international consultancy and think tank specialising in analytical advisory services to Government, Investment Banks and International Financial Institutions. He worked for the World Bank in Afghanistan and India as an economist and as an Senior Advisor to the Government of the Afghanistan on the Afghan National Development Strategy and Afghanistan Compact where he worked as an advisor to Presidents Office. In his time at the World Bank he pioneered the Bank's work on public finance management in the area of national security and subsequently introduced the concept of 'right-financing' of public finances for national security in support of Fiscal Sustainability. At its core, the concept of rightfinancing, as applied to national and human security, is fundamentally about determining security as a sustainable public good, with relevance to good governance and oversight and accountability mecahnsims and prioritization mechanisms and processes that support increasingly higher quality security services over time.