The final chapter in this book makes the case that although development agencies of all kinds have become a global phenomenon, there has been limited international exchange on how and why such organisations work. It explains that though the codification and sharing of practice is inherently difficult, the purpose of this book is to attempt to bridge part of that gap and promote understanding within a shared framework and the learning of precise lessons across borders. To conclude, a series of development agency strengths and constraints are defined and illustrated which inform the OECD LEED Programme’s ten principles for development agencies.