Recently we have been investigating low-temperature synthesis routes to prepare novel complex transition metal oxide phases with highly unusual oxidation states and/or coordination geometries.Reduction of the Ruddlesden-Popper phase Sr2VO4 with CaH2 produces Sr2VO3, which X-ray powder diffraction data indicates adopts a crystal structure analogous to that of orthorhombic Sr2CuO3. This would suggest the V2+ cations in this material adopt a square-planar coordination environment. To the best of our knowledge this is the first time a square-planar vanadium centre has been observed in an extended oxide, and possibly the only example of a square-planar V2+ centre in any chemical system.We propose to collect neutron powder diffraction data from Sr2VO3 and the related phase Sr3V2O5.8 to confirm the crystal structures of these phases and thus the vanadium coordination geometries adopted