The Second Vatican Council is recognised by the Roman Catholic Church as the twenty-first ecumenical council. The largest in terms of participants and one of the longest-running, it also covered the widest range of topics and produced the largest volume of documents and decrees. This article, based on the text of the ninth Lyndwood Lecture, examines a number of characteristics of Vatican II in comparison with previous councils, arguing that, while in many ways Vatican II was novel, in its composition, agenda, influence and reception one can discern parallels with past councils back as far as the first ecumenical council at Nicea in 325.1