In recent years on JET, technological upgrades in the field of diagnostics have been focused mainly on the measurements of fusion products and plasma wall interactions. Neutron spectrometry has been improved with the installation of a high resolution time-of-flight neutron spectrometer, an upgrade of the Magnetic proton recoil spectrometer and a coherent development strategy for compact spectrometers (NE213 liquid scintillators and diamond detectors). For fast particles, g-ray spectrometry is being upgraded with the addition of neutron attenuators, based on both pure water and LiH and the installation of better detectors using high-Z scintillator materials. Significant attention has also been devoted to testing radiation hard detectors, ranging from Chemical Vapour Deposited diamond detectors for neutron counting to Si-on-insulator technologies for particle detection and innovative Hall probes for the measurement of steady-state magnetic fields. To improve the diagnostic capability for measuring erosion and redeposition at the first wall, first, very encouraging, results have been obtained with Laser Induced Break-down Spectroscopy. Significant progress has been made with a test programme of mirror materials for ITER.