The paper discusses recent progress in fusion physics on the Joint European Torus (JET) in the fields of plasma confinement, MHD stability, particle and power exhaust, and fusion performance and a-particle effects. In this context results are presented from the three JET operating regimes: ELM-free H-mode, ELMy H-mode and optimised shear mode. These results together with those from other tokamaks form a sound basis for extrapolation to a Next Step device based on ELMy H-mode operation and point the way for the development of more advanced tokamak scenarios.