CERN staff and their families were joined by numerous distinguished guests for the official ceremony that launched civil engineering work for the Large Electron-Positron (LEP) collider project on 13 September 1983. Speeches by Herwig Schopper (CERN’s Director-General) and Presidents François Mitterrand and Pierre Aubert were followed by an inaugural ceremony then music and celebrations on the lawn.   With a circumference of 27 km, LEP was the largest electron-positron accelerator ever built, and excavation of the LEP tunnel was Europe's largest civil-engineering project prior to the Channel Tunnel. LEP operated for 11 years from July 1989 until its closure on 2 November 2000 to make way for construction of the Large Hadron Collider (LHC) in the same tunnel.