After a five year construction phase, the Joint European Torus produced its first plasma on June 25, 1983. This represented the culmination of considerable effort on the part of all concerned and was according to the plan established at the commencement of the JET Joint Undertaking in June 1978. In particular, the installation of the machine itself began in January 1982 when the torus hall was handed over (building construction began in May 1979), and the first machine octant was installed in August 1982. The final machine octant was placed in position in December 1982. Since then, commissioning of many of the subsystems has taken place, leading to the first plasma, and subsequently to a limited amount of "exploratory" machine operation.