Since early 2000, the JET-Enhanced Performance (JET-EP) programme has been aiming at optimising JET for ITER-relevant plasma operations, from 2005 onwards. The overall heating capability of JET will be increased to 40MW by upgrading the neutral beam system and building a new ITER-like ion cyclotron radio-frequency heating (ICRH) antenna with particularly stringent specifications. The new divertor will be able to absorb more than 300 MJ per shot and allow running high-triangularity ITER-like scenarios with a greater flexibility with respect to different plasma configurations. The control of extreme plasma shapes will be reinforced and a new disruption mitigation system using a very fast gas valve will be provided. The diagnostic capability will be enhanced by several new systems designed to address a number of crucial physical phenomena for ITER. To study tritium retention further, new technologically challenging erosion-redeposition diagnostics will be installed, particularly in the divertor region, both real time and integrating...