sentences:  In the third phase, during the later 1270s and the early 1280s, the two eastern bays of the northern side of the nave were built, as well as the adjacent chapel of Saint Fulcran, the portal and its porch.The choir was vaulted, and temporarily closed off so that it could be used for services.In a fourth phase of about 1295/1300 the north side was completed, with the chapel of Saint Martin (now the chapel of Saint Roch), and work on the south side was begun with the Lady Chapel and the chapel of Saint Michael, above which was built a belltower over 57 metres high, which also served as a watch-tower.