The Black Book of the Admiralty is a late medieval Old French manuscript containing a variety of documents relating to the administrative and legal responsibilities of the office of the lord high admiral, with later additions relating to the court of chivalry and the laws of war. The edition of this manuscript produced by Sir Travers Twiss (1809–97) between 1871 and 1876 filled only part of one of four volumes. The remaining content ranges from the late thirteenth-century borough custumal of Ipswich and other later medieval general custumals from south-west France, to a variety of different codes of maritime law also from south-west France, Catalonia, southern Italy, the Baltic and the crusader kingdom of Jerusalem. Volume 4 contains a fourteenth-century procedural code relating to the maritime court of Valencia and late medieval codes of maritime law from the Mediterranean and the Baltic, as well as a Flemish version of the laws of Oleron.
