The effect of cooling flow and its interaction with the gas path upon the flow and heat transfer within turbine disc cavities has been investigated within the five-year European Union funded research project MAGPI. This paper describes a part of the conjugate CFD analyses and validation work performed by Siemens within this research project. Validation is based upon measurement data from a dedicated two-stage axial turbine rig at the University of Sussex. A conjugate CFD model of the turbine was produced including the gas path and all disc cavities using the commercial CFD solver ANSYS CFX 12.1. The SST k-w turbulence model has been used for much of the work. Comparisons are made to the k-e model and the more complex Reynolds Stress models. Transient and steady-state solutions are also compared and the predictions are compared to the data from the test rig. Good agreement between predicted and measured air temperatures and pressures in the turbine cavities and stator well are found for the most part, even on quite coarse meshes. Metal temperatures compare well in many places with a prediction of the absolute temperature to within a small error. There are however some regions on the first stage rotor where a reasonable difference between predicted and measured metal temperatures is consistently observed regardless of turbulence model, simulation type (steady-state or transient), and mesh density.