In 1993, the Common Core of European Private Law project was launched. Ever since, three groups convene every year to discuss themes to be taken up. In the group on contract law, the theme of unexpected circumstances was suggested on various occasions. As a matter of fact, one of the hypothetical cases dealt with in the very first theme that led to a published volume was about change of circumstances. In 2001, the general editors of the series, Mauro Bussani and Ugo Mattei, asked Ewoud Hondius, later to be joined by Hans Christoph Grigoleit, to set up a group on this subject. National reporters were then selected, both from within the Trento/Torino participants and from outside the group.

At the group's first meeting in 2001 reporters for Belgium (Luc Vael), France (Anthony Chamboredon) – both later replaced by Denis Philippe (Belgium) – Germany (Carsten Herresthal), Italy (Francesco Macario), the Netherlands (Mirella Peletier, later replaced by Willem Wiggers), Portugal (Júlio Gomes and Antonio Pinto Monteiro) and Sweden (Bert Lehrberg) discussed a questionnaire to be sent out. During the meeting or at later stages, the charter members were joined by members for Austria (Brigitta Lurger), the Czech Republic (Luboš Tichý), Denmark (Kim Østergaard), England and Ireland (Robert Clark and Cliona Kelly), Greece (Anastassios Valtoudis), Lithuania (Valentinas Mikelenas), Scotland (Laura Macgregor), Slovenia (Matjaž Tratnik) and Spain (Odavia Bueno Diaz and Luz Martinez Velencozo).