A new ex vessel magnetic diagnostics was installed in JET during 2005 shut down, with the objective of: i) provide experimental data for a better modelling of the iron in the axisymmetric codes for plasma equilibrium reconstruction; ii) test the reliability of direct field measurements from Hall probes. The latter are of great interest for future ITER-like devices, where long lasting flat top phases are expected, in a high neutron yield and a high temperature environment. The experimental data achieved during the restart phase were analysed with the aid of simulation codes. Each individual signal was assessed for inclusion in the general JET Diagnostics system. The system is ready for use in the 2006 experimental campaigns.