BiFeO3 is by far the most widely studied multiferroic material and yet many mysteries remain in the phase diagram. One mystery is the crystal structure of the high T gamma phase. Previous work by us has demonstrated that this phase is not cubic as previously reported. More recently we have shown that the gamma phase of BiFe0.7Mn0.3O3 is also not cubic and is better described by the space group Rbar3c. However, this symmetry does not seem to satisfy the data collected for BiFeO3. We propose to investigate the high T phase diagram of Mn doped BiFeO3 with the aim of elucidating this unusual behaviour further. In addition we aim to probe the isostructural Bi1-xLaxFeO3 system. Conducting these experiments at the same time will allow us to investigate the effects of A- and B-site doping ultimately gaining a better understanding of not only both of these systems but also BiFeO3.