A large amount of Public Sector spatial data has been created in and is managed in ArcGIS. This has often been seen as an impediment to providing universal access to that data, but in fact in this deck I argue that the opposite is true. In recent years Esri software engineering effort has resulted in the adoption of open standards across the ArcGIS Platform that in turn make it possible to support our Customers as they seek to make more and more of their data available as either INSPIRE services or OpenData. This has resulted in a number of interesting Projects, both commercial and Open Source that have truly "opened ArcGIS". This deck presents some aspects of that transformation, examines the resulting projects and consider future developments and of course has a bit of personal reflection thrown in for good measure!