Scientific and technical activities on JET focus on the issues likely to affect the ITER design and operation. Understanding of the ITER reference mode of operation, the ELMy H-mode, has progressed significantly. The extrapolation of ELM size to ITER has been re-evaluated. Neoclassical Tearing Modes have been shown to be meta-stable in JET, their beta limits can be raised by destabilisation (modification) of sawtooth by ICRH. Alpha simulation experiments with ICRH accelerated injected 4He beam ions provide a new tool for fast particle and MHD studies, with up to 80–90% of plasma heating by fast 4He ions. With or without impurity seeding, quasi-steady state high confinement (H98 = 1), high density (ne/nGR = 0.9–1) high β (βN = 2) ELMy H-mode has been achieved by operating near the ITER triangularity (δ ~ 0.40–0.5) and safety factor (q95 ~ 3), at Zeff ~ 1.5–2. In Advanced Tokamak scenarios, internal transport barriers (ITBs) are now characterised in real time with a new criterion, ρ*T. Tailoring of the current profile with LHCD provides reliable access to a variety of q profiles, lowering access power for barrier formation. Rational q surfaces appear to be associated with ITB formation. Alfvén cascades observed in Reversed Shear plasmas, providing identification of q profile evolution. Plasmas with 'current holes' were observed and modelled. Transient high confinement Advanced Tokamak regimes with H89 = 3.3, βN = 2.4 and ITER relevant q < 5 were achieved with reversed magnetic shear. Quasi-stationary internal transport barriers are developed with full non-inductive current drive, including ~50% bootstrap current. Record duration of ITBs was achieved, up to 11 s, approaching the resistive time. For the first time, pressure and current profiles of Advanced Tokamak regimes are controlled by a real time feedback system, in separate experiments. Erosion and co-deposition studies with the quartz-micro-balance show reduced co-deposition. Measured divertor thermal loads during disruptions in JET could modify ITER assumptions.