In the early 1970s, two CERN Laboratories existed side by side at Meyrin and Prévessin. The Prévessin (France) site, where the Super Proton Synchrotron was located, remained under the leadership of John Adams as Director-General of CERN Laboratory II. Willibald Jentschke became Director-General of CERN Laboratory I (Meyrin, Switzerland) in January 1971 - December 1975.