Recently, at Princeton University, USA, plasma temperatures in the region of 60 million degrees Kelvin were attained in a fusion experiment of the so-called tokamak type. This was a significant advance over the temperatures (about 25 million degrees) previously achieved after years of research effort. In other tokamaks record values of the thermal insulation have recently been achieved Consequently there are good prospects of reaching both the temperatures and thermal insulation together needed for power production What then stands between us and the achievement of controlled nuclear fusion power?