This Fusion Diagnostic Group develops, maintains and uses diagnostics to study the neutron emission from nuclear fusion reactions occuring in controlled thermonuclear fusion plasmas. The group has installed two neutron spectrometers at JET and it is actively involved in the energetic particle physics studies. The group is developing, in collaboration with UKAEA, a new neutron camera for the MAST experiment and it is involved in the design of neutron spectrometers for ITER.The reasearch activity is funded from VR and EFDA.