Rector Dr. Christiaan Alting von Geusau, himself an alumnus of Leiden University, participated with his father, also an alumnus and a retired professor of the same institution, in the tradition-rich annual commemoration of the founding of the University of Leiden on 8 February 1575 by Prince William of Orange and the States General of Holland and Zeeland. The founding of the university was a reward for the people of the City of Leiden for their brave stance in ejecting the Spanish occupiers the year before on 3 October 1574 ("Het Leidens Ontzet"). More than 200 professors from Leiden and beyond participated in this oldest of annual academic traditions by processing after the university rector, deans and visiting rectors from the Academiegebouw (Academy Building, gifted by The Prince of Orange to the newly founded University in 1575) to the Pieterskerk (the former St. Peter's church) in Leiden where the formal celebration was held. The official University of Leiden video of the event can be seen here. A local photographer's impressions of the Leiden University Dies natalis 2017 can be found here.