International audience Many small ports dot the left bank of the Seine estuary among which Honfleur becamùe dominant. Tidal movements created uncertainty as to the contours of the seacoast and estuary’s shoreline, its economic potential and necessitated an exact geography of the extent of local jurisdictions. Local sources bear witness to conflicts over borders and between local lords. During the 13th century, the Bertran, lords of Honfleur, tried to assert their preeminence and develop the port’s activities. This was not easy given the rivalry with other jurisdictions, notably that of the Crown.