A hollow current profile is observed to form in the early stages of the Canberra tokamak LT-3. A helical perturbation appears, of the mode predicted by resistive MHD theory (m = 4, n = 1) for the measured q-profile. Subsequently, the plasma relaxes rapidly to a state of approximately uniform current. Runaway electrons diffuse very rapidly during this period with step sizes round the torus of up to 1 cm. These are indicative of a disruption of the magnetic surfaces, probably as a result of the growth of the helical perturbation.