Our knowledge of the period of European history conventionally called the Middle Ages rests, in a large part, on the writings that survive from that time, all of them manuscript. In this talk PROFESSOR ROBERT BARTLETT, Emeritus, University of St Andrews, explores cases in which large numbers of such manuscripts were destroyed in a day, not by accident of fire or flood but by human destructive force – arson, shelling and bombing. It will look at the political and military events that led up to the moment of destruction, the nature of the material that was lost and how it came to be where it was. Finally, more cheerfully, there is discussion of the heroic efforts made by scholars and archivists to save something from those catastrophes. Historical knowledge rests on material remains, which include manuscripts, and they are vulnerable.