While carrying out surface surveys, a group of co-workers from Snecma at Corbeil-Essonnes found a large quantity of knapped flint in a ploughed field near the Seine, at Étiolles. They realised that their discovery was likely to indicate a prehistoric site and alerted the regional archaeology department at the Ministry of Culture. In 1971, with the help of these amateurs, the department began a preliminary excavation, and the amateurs proved to be correct. An excellent example of a fruitful collaboration between amateur and professional archaeologists.