This report provides the rationale for policy engagement as well as practical guidance for both investors and policymakers. This guidance is based on a review of the experiences and lessons learned from five case studies in which investors were engaged in the policymaking process. In each case, investors and policymakers were interviewed to understand the origins and motivations of the policy measure, the engagement process, the influence of investors on the policy process, the lessons learned and, where available, the outcomes achieved. This report will be used to frame and direct the PRI’s Policy and Research workstream which was set up in 2013 as it looks to encourage investor engagement in policy.