On the night of February 12, 1322, the eve of S. Ermenilda's day, the central tower fell. Its insecurity had long been known. The monks had just left their matin service in S. Catharine's Chapel. Some persons conclude from this fact that the choir had already been disused as being unsafe; but unless there is other evidence of this, the mere fact of the monastic matins being held in the chapel nearest to the domestic buildings seems hardly sufficient to justify the conclusion. The chapel here named was not (according to Dean Stubbs) the one now dedicated to S. Catharine at the west end of the cathedral, but one that adjoined the chapter-house. The fall of the tower destroyed three bays of the choir. Different opinions are held as to the character of the architecture of the bays thus destroyed. Some hold that Bishop Northwold built the choir and presbytery, from the central tower to the east end, in the Early English style, and that three of his bays were thrown down by the fall of the tower[9]; others think that the bays now ruined were part of the Norman work.[10] It is most probable that Northwold, designing to increase the length of the presbytery, only pulled down so much of the Norman work as was necessary for his purpose, leaving the western arches standing. This opinion is adopted in the account of his work given above. If this is correct, there would have been _four_ Norman arches left standing between the tower and the Early English work. Of these, three on each side fell. When the new choir was constructed, the octagon taking up the space of the first bay, the fourth bay--presumably left uninjured--was removed, as being out of keeping between the Early English and the new Decorated bays; and hence three new bays were built, reaching to Bishop Northwold's work. All accounts agree that _three_ bays were destroyed. But if both choir and presbytery were of Early English date, there must have been _four_ bays overthrown, because the three Decorated bays now existing do not correspond in position to the three destroyed, for the present third bay from the screen is where the fourth bay was when the tower was standing.