Neutrons are produced in fusion energy experiments with both Deuterium (D) and Deuterium -Tritium (DT) plasmas. Neutron spectroscopy is a valuable tool in the study of the underlying fuel ion populations. The Magnetic Proton Recoil neutron spectrometer, originally installed at JET in 1996 for 14MeV neutron measurements, has been upgraded, with the main aim to improve its Signal-to-Background ratio (S/B), making measurements of the 2.5MeV neutron emission in D plasmas possible. The upgrade includes a new focal plane detector, based on the phoswich technique and consequently less sensitive to background, and a new custom designed digital data acquisition system based on transient recorder cards. Results from JET show that the upgraded MPRu can measure 2.5MeV neutrons with a S/B = 5, an improvement with a factor of 50 compared to the original MPR. A S/B of 1.4×104 in future DT experiments is estimated. The performance of the MPRu is exemplified with results from recent D plasma operations at JET, both concerning the new 2.5MeV measurements with Ohmic, RF and NB heating, as well as 14MeV measurements of tritium burn-up neutrons. The upgraded instrument allows for 2.5MeV neutron emission and deuterium ion temperature measurements in plasmas with low levels of tritium, a feature necessary for the ITER experiment.