RDT is a graphical formal modelling language in which the modeller works by constructing diagrams of the processes in their model which they then join together to form complete systems. Aside from the benefits which accrue as a side effect of building a formal model of a proposed system, these diagrammatic models can be useful as a means of communication between the development team and the users. However one of the greatest benefits of a formal model is that it can be subjected to rigorous examination to ensure that it satisfies properties required of the system.This paper describes the transformation used by the RDT toolset to generate Promela code (the input language of the SPIN model-checker) automatically from a model.