The recent JET D-T experiments provided many results useful to the preparation of fusion power plants, thanks to its tritium handling capabilities, size and metal wall. This talk will provide a brief introduction to JET and its improved capabilities compared to the previous high power D-T experiments in 1997. Selected plasma physics results (impact of isotope mass, alpha particles) addressing questions of interest to fusion power plant will be presented. The strategy for preparing, in deuterium and in tritium, the JET plasma operational scenarios required for high D-T fusion power will be discussed, along with the results. The JET D-T neutron fluence is relevant to that beyond the breeding blankets in next step fusion devices. This provided a rare opportunity for testing fusion materials and components in a tokamak environment, as part of a wide-ranging neutronics programme, with representative results presented here.