This book celebrates the publication of the early fifteenth-century inquisitions post mortem (IPMs) and seeks to ensure their exploitation as widely and profitably as possible. It sets the agenda for the much fuller exploitation of a key source for many aspects of the late medieval English economy and society and sets out the rewards of more sustained study of the IPMs. Of all twenty-nine volumes of calendars (CIPMs), it is volumes xxii–xxvi that are the most comprehensive and those best attuned to the interests of twenty-first-century users. The Arts and Humanities Research Board (now Council), the National Archives, the University of Cambridge, Professor Christine Carpenter as editor, and Drs Matthew Holford, Claire Noble, Kate Parkin, and Stephen Mileson deserve the grateful thanks both of specialists on fifteenth-century history and of that much wider community of researchers (often recreational) who can now fully exploit this wonderful material. This Companion needs to reach that host of local historians and genealogists for whom IPMs are a crucial but often unrecognised resource. Calendaring of the IPMs has stopped, one hopes temporarily, with the inquisitions post mortem for 1447–85 uncalendared. In the meantime, Professor Michael Hicks is leading the AHRC-funded project to digitise the twenty-nine volumes and make them freely accessible – volumes i and ii are already on British History Online – and to convert volumes xviii–xxvi into a fully interactive web-mounted resource that will permit analysis which is currently extremely difficult and laborious.