The presidents of CERN’s two host countries, François Mitterrand of France and Pierre Aubert of Switzerland, symbolically broke the ground and laid a plaque commemorating the inauguration of the Large Electron–Positron collider (LEP) on 13 September 1983.

Although much of the necessary infrastructure for the new accelerator was already in place (such as CERN’s existing accelerator complex to pre-accelerate the electrons and positrons for LEP), many new facilities were needed. The most obvious of these was the 27-kilometre tunnel that housed the machine, along with the experimental halls and surface buildings. Transfer tunnels joining the Super Proton Synchrotron to LEP were also needed, as were buildings to house a linear accelerator (linac) and storage rings to make and accumulate electrons and positrons. Despite the huge scale of the undertaking, progress was impressive. By the end of 1984, the buildings for the linac and the electron–positron accumulator were complete and ten of the 18 access shafts had been excavated.