Some recent JET campaigns, with the introduction of a trace amount (nT/nD < 5%) of tritium into D plasmas and third harmonic ICRH acceleration of 4He, provided unique opportunities to test 'burning plasma' diagnostics. In particular, new approaches and techniques were investigated for the detection of neutrons, α particles and the fuel mixture. With regard to neutron detection, the recent activity covered aspects such as calibration and cross validation of the diagnostics, measurement of the spatial distribution of the neutrons, particle transport and neutron spectrometry. The first tests of some new neutron detection technologies were also undertaken during the Trace Tritium Experiment campaign. To improve JET's diagnostic capability in the field of α particles, a significant development programme was devoted to the measurement of their confinement and imaging with γ-ray spectroscopy. A new approach for the fusion community to measuring the fast ion losses, based on the activation technique, was also attempted for the first time on JET. An assessment of the neutral particle analyser's potential to determine the fuel mixture and the particle transport coefficients is under way.