The most important surviving documentation concerning the succession case arising from the death of Duke John III of Brittany in 1341 consists of the arguments put forward in the names of John de Montfort and Charles de Blois (on behalf of his wife Joan de Penthièvre), the two chief contenders for the ducal title, and the procès-verbal of the interrogation of witnesses brought to testify about these arguments. Montfort's case, presenting reasons why Philip VI of France should allow him to do homage for Brittany, can be found in two contemporary copies, first, Archives départementales de la Loire-Atlantique, Nantes, E 6, which is the chief text edited here, and secondly, Archives Nationales, Paris, J 241, no. 44. There is also an abridged Latin version of Montfort's case in another contemporary copy, Archives Nationales J 241, no. 44bis. The arguments of Blois can now be found only in a late sixteenth-century copy, probably made by the celebrated Breton jurist, Bertrand d'Argentré (1519–90). Similarly a transcript or precis of the interrogation can be found only in d'Argentré's notes and in those of the antiquarian and genealogist, André Duchesne (1584–1640), these two manuscripts being respectively Bibliothèque Nationale, fonds français, nos. 18697 and 22338. Several copies exist of these documents, the chief amongst them being a copy of Archives Nationales J 241, no. 44 made following a commission issued in the Parlement of Paris on 15 January 1652 and now contained in Bibliothèque Nationale, MS. Nouvelles acquisitions françaises 7270, and another seventeenth-century copy of the same document, now British Museum, Additional Manuscript 30752.
