A team photo celebrates  the completion of the SPS tunnel in July 1974. The Super Proton Synchrotron (SPS) was the first of CERN’s giant accelerators. It was also the first cross-border accelerator. Excavation took around two years, and on 31 July 1974 the Robbins tunnel-boring machine returned to its starting point having crossed the Franco-Swiss border and excavated a tunnel with a circumference of 7 kilometres and an average depth of 40 metres below the surface.   The SPS was commissioned in 1976, and a highlight of its career came in 1983 with the announcement of the Nobel Prize-winning discovery of W and Z particles.