The ERFA is a major part of the upgrade to the plasma vertical stabilisation system for JET. As well as improvements to the plasma controller, there was a requirement for a new power supply with increased voltage and current capability over its predecessor the Fast Radial Field Amplifier (FRFA).The ERFA had to be factory tested, installed at JET, power and signal connections made, all signals tested and then installed adjacent to FRFA. The connection to the JET coils had to be achieved in a planned 7-week pause in operation dedicated to this installation activity and perform to its full capability from the JET restart. The ERFA project achieved all of its aims and, following a minor upgrade, met or exceeded the performance specifications.