Cubic double perovskites provide a rare example of an undistorted face-centred cubic lattice, made up of edge sharing regular tetrahedra. In Ba2MnWO6, antiferromagnetically coupled S=5/2 Mn2+ ions are situated at the vertices of these tetrahedra, in an arrangement in which the magnetic interactions cannot all be simultaneously satisfied. This geometric frustration gives rise to highly unusual magnetic ground states, which often retain some dynamic behaviour. This proposal seeks to determine the nature of the magnetic ordering in Ba2MnWO6 and how this is disrupted on doping with the smaller A-cation, Sr2+, inducing structural distortions away from the cubic end member.