Bulk high temperature superconductors are useful for permanent magnet applications because they can generate much stronger magnetic fields than ferromagnets and are more compact than wound magnets. These properties can be exploited in electrical machines with high power-to-weight ratio for the aerospace industry and in biomedical applications such as MRI and novel magnetic drug targeting therapies. When magnetised, these ceramics are subjected to considerable internal tensile stresses. Their poor mechanical properties in tension result in the magnets failing as a result of cracking before their maximum field is reached. We will measure the elastic strains in the different phases of superconducting bulk magnets during and after energisation in an external magnetic field using in-situ neutron diffraction and will correlate this with numerical models to determine the onset of cracking.