The Internet of Things is anticipated to deliver significant innovation in many different areas, including future cities, transport, health and social care, manufacturing, and agriculture. Sensors can be deployed at low cost to instrument the world to a far greater extent than has hitherto been possible. There is increasing recognition of the potential value in breaking down data silos and opening up data resources so that they can be exploited more fully. However, the IoT exhibits considerable diversity and complexity which means that significant barriers to innovation remain. This paper report on BT's experience in creating and supporting IoT ecosystems of data providers and consumers, using the CityVerve Smart City project as an exemplar.