The evolution of the current and temperature profiles in JET has been analysed using current profiles derived from advanced equilibrium analysis codes, and temperature profiles obtained from absolutely calibrated ECE measurements. It is found that current evolution during the discharge 'flat-top' is well described by neoclassical, rather than Spitzer, resistivity. During the current rise phase however, current penetration is substantially more rapid than expected. The mhd processes influencing the rapid penetration are discussed, and a new analysis of this mhd activity based on the trajectories of discharges in the (qo,qa) plane is presented.