Tungsten Tellurites are being used to make optical fibres that transmit light into the mid infra red. However, not much is know about the structure of these glasses. We wish to better understand the interaction between tungsten atoms and the tellurite glass network. The aim is to relate structural changes arising from the addition of tungsten oxide to functional properties, such as Tg, density and refractive indices. The good sensitivity of neutrons to tungsten, tellurium and oxygen will enable all the short range correlations in the glass to be measured with equal weighting. When combined with X-ray correlation functions and anomalous x-ray correlation functions at the W K-edge (time applied for I15 diamond), it will be possible to characterise the tellurium-oxygen and tungsten-oxygen environments to be characterised by extracting bond lengths and coordination numbers.