There is a significant interest in the electronic and magnetic properties of the layered iridates owing to the variety of potential exotic phases of matter they exhibit. In particular, the parent phase Sr2IrO4 exhibits a spin-orbit Mott state, which is destroyed by a low level of either doping or oxygen deficiency. We propose to study the magnetic properties of the compound Sr2Ir0.5Rh0.5O4, which is an Anderson localised paramagnet with an uncharacterised, highly frustrated low-temperature magnetic phase, by means of high-resolution magnetic neutron diffraction. These measurements are part of a wider EPSRC-funded research project on 5d oxides that has already produced significant results.