This proposal is part of our research programme on spin and orbital order in frustrated systems. The spinel FeSc2S4 realises an exotic ¿spin-orbital liquid¿ with no magnetic or orbital order down to mK temperatures, in spite of strong inter-site interactions. Fe2+ ions located on a diamond lattice have both a spin and an unquenched orbital degree of freedom, and in the absence of spin-orbit coupling one would expect both magnetic and Jahn-Teller orbital order. The absence of both orders points to the importance of spin-orbit coupling in stabilizing this unusual state. We have a high-purity powder sample of FeSc2S4 and here we propose to use the high-flux Merlin spectrometer to measure via neutron scattering the full spectrum of energy levels of the Fe2+ ions stabilized by the spin-orbit coupling and local crystal field to find all relevant terms in the microscopic Hamiltonian.