The concept and the key features of the Joint European Torus (JET), flagship of the integrated European fusion research programme, departed considerably from those of other large tokamaks under design in the early 1970's. D-shape toroidal coils, vacuum vessel and plasma with large volumes and currents were unique and controversial features of JET. Moreover, since the early phase of the JET design, due consideration was given to D-T operations, including remote handling capability and D-T compatible peripheral systems. JET experimental results have confirmed the validity of these design choices. In tum, these choices had an impact on the development of other tokamaks and of 'next step' design proposals, such as NET (Next European Torus) and later ITER (International Tokamak Experimental Reactor). Experimental evidence from JET and other tokamaks has clearly shown that the control of impurities is a key issue for finalizing the ITER design. Therefore, the present JET programme is focussed on a Divertor Programme, with thermonuclear grade plasmas, tailored to ITER needs.