In the late 1970s physicists from CERN Member States were discussing the long-term future of high-energy physics in Europe. A new picture of fundamental processes – unification – was emerging and the Large Electron–Positron collider (LEP) would be the machine to study it. After a history built on proton accelerators, the idea of an electron–positron collider was a break with tradition for CERN. But since the results of electron and positron collisions are far easier to interpret than collisions between protons and antiprotons (which were on CERN’s more immediate horizon with the UA1 and UA2 experiments), the LEP proposal won through.

Presenting the project to CERN council, CERN Director-General Herwig Schopper reviewed the scientific justifications, budget and construction timetable for LEP. He concluded that:

Very rarely in the past has there been so much unanimity and so much consensus amongst the European scientific community on the validity of a research instrument.

The accelerator was formally approved on 22 May 1981.