The particle and energy transport properties of the high fusion performance JET pulses that were obtained before and during the first tritium experiments are discussed. The particle diffusion coefficient of tritium is determined by monitoring the decay of a small quantity of injected tritium in a deuterium background plasma. A good simulation of the measured 14MeV emissivity profile is obtained throughout the decay phase, if the mixing of the two species is described by a model in which the tritium diffusion coefficient is similar to that of the deuterium. The energy confinement of these low density hot-ion H-mode discharges is found to have both improved central and edge confinement over the conventional medium to high density H-mode discharges. Enhancement factors of at least twice the value predicted by H-mode scaling expressions are observed transiently. A local transport analysis is completed to try and establish the reason for the improved confinement. Several possibilities are investigated, including stabilisation of the hi mode by the peaked density profile and access to the second ballooning mode stable region. Finally, for the discharge with a high concentration of tritium, it has been suggested that a-particle driven instabilities could affect the energy confinement. A comparison is made with the stability threshold of toroidicity induced Alfven eigenmodes (TAE) and the a-particle statistics are presented.