In 1439, Granville and its small fishing village were sold to the English. In control of all of Normandy except Mont-Saint-Michel and the island of Tombelaine, they needed a stronghold in the bay. In 1440, a trench 22 ft (7m) wide and 59 ft (18 m) long transformed the Granville peninsula into an island, and the construction of the 1,640 ft (500m) long ramparts began. The unfinished fortress was taken over by the French troops from Mont-Saint-Michel in 1442. Over time, the moat was filled in, and the walls raised.