In the course of 2.5 years research in Cambridge, we have developed for the first time a tough, low-carbon martensitic stainless steel weld metal (CamAlloy 4) which can be used to mitigate residual stresses in the welding of austenitic stainless steel components. Stainless steel or mild steel plates welded using this new alloy, suffered substantially less distortion than those welded using conventional weld metals. It is now essential to assess the performance of the new alloy in reducing residual stress by measuring the residual stresses developed in thick welded plates. The outcome of the neuron diffraction tests will provide valuable information which is required for further development of the new alloy and validation of our models for material behaviour during welding.