The UK experienced widespread and disastrous flood events in 2007 and 2010, and the future incidence of flooding is predicted to increase. Understandably much media attention and research has focused on the impacts on people, their homes and jobs, and the future implications for flood risk insurance that has been a feature of the UK market. Research on flood risk and property undertaken at the College of Estate Management in 2006 found very little literature covering the effect of flooding on commercial property and the risks to property investment. Property is an important diversification asset in investment portfolios that underpins pensions, insurance and savings plans. Investors surveyed reported undertaking flood risk assessments in conjunction with property acquisitions, but none reviewed the flood risk status of property held in their portfolio, although they monitored other aspects of building performance. This is now changing and the IPD sustainable property index has introduced flood risk monitoring. This paper is based on research in 2010-2011 that examines the process of due diligence for flood risk adopted by commercial property investors to identify risks, inform purchase decisions and devise subsequent actions geared to mitigating and managing flood risk. Case studies illustrate the process, derived from interviews with major investment funds, their professional advisers and other stakeholder representatives, including environmental consultants, valuers, solicitors, lenders and the insurance industry. The paper explores the challenges to investment decision making and property valuation, given continuing uncertainties associated with flood risk predictions. The case is made for further research to establish the extent of UK investment property potentially at risk from flooding, the degree of risk to which it is exposed and to inform the way in which the risk is translated into valuation. Property represents about 4% of total investment assets under management in the UK (and 2.8% in the institutional market), but is significant in absolute terms given a market value estimated by IMA at ¬£4.4trn. About 20% by value is in central London, known to be one of the most at risk cities globally for flooding ìì but there is otherwise no clear picture of where and how much commercial investment property could be at risk. This paper makes the case for finding out.