Disclosed herein is a toroidal field coil for generating a toroidal magnetic field in a nuclear fusion reactor comprising toroidal plasma chamber having a central column, the toroidal field coil comprising a plurality of windings passing through the central column and around the outside of the plasma chamber. Each winding includes a cable comprising a plurality of stacked HTS tapes, each HTS tape including one or more layers of a high temperature superconductor material. The HTS tapes are arranged such that a face of each HTS tape is parallel to the toroidal magnetic field as the cable passes through the centre column