The material to be studied is nuclear graphite used in the core of operating Advanced Gas-cooled Reactors (AGRs) in the UK. It is a non-replaceable component and therefore life-limiting. Understanding the deformation and fracture of the graphite, especially at high temperatures that are relevant to service, will help to maintain safe generation of energy to keep the UK's lights on. We propose to deform graphite samples at high temperature (up to 900degC), and measure the lattice spacing change in the material using neutron diffraction. This change of the lattice space will be compared with the bulk deformation and this will provide precious insight to the understanding of its high temperature behaviour. This is the first attempt to investigate nuclear graphite using neutron diffraction at high temperature; the outcome will provide strong basis for forward structural integrity prediction.