Experiments in the ELM free hot ion H mode regime have been carried out in DT plasmas in JET. Initial experiments undertaken at constant neutral beam (NB) power (∼11 MW) demonstrated that core fuelling was dominated by wall/target recycling rather than NB fuelling and made it possible to arrange an optimum core DT mix by adjusting the DT mix in wall/target, gas and NB. High power experiments at 4.2 MA/3.6 T have successfully and reliably delivered fusion power (Pfus) up to 16.1 MW and plasma stored energy (Wdia) up to 17 MJ. The results are in good agreement with extrapolations, carried out with the TRANSP and JETTO codes, from similar deuterium discharges. Transiently, values of Qtot up to 0.95 ±0.17 were achieved, consistent with values of nDT(0)τE, diaTi (0) ≈ 8.7 × 1020 m-3·s·keV±20%. The ratio of fusion power to input power, Qin, is in excess of 0.6. There are indications of an isotope effect on the edge pressure pedestal, but no net dependence of global confinement on isotopic plasma composition has been found.