In this paper we present an original method of analysing the newly-revised UML2.0 activity diagrams. Our analysis method builds on our formal interpretation of these diagrams with respect to the UML2.0 standard. The mapping into another formalism is the first stage of a refinement process which ultimately delivers derived analytical results on the model. This process highlights latent performance problems hidden in the high-level design, allowing software developers to fix these design flaws before they are concretised in implementation code. We exercise our analysis approach on a substantial example of modelling a multi-player distributed role-playing game.