The mere fact that the detached tower was built suggests many questions which are not easily solved. Why was it at all necessary? Perhaps the cathedral bells hung in the south-west tower, and those of the sub-deanery church in the other, or _vice-versa._ At all events, we know that in the fifteenth century the sub-deanery church was removed from the nave to the north arm of the transept. The great window of the north end of the transept is also early fifteenth century in date, and the detached tower likewise. Angle turrets were placed upon the four angles of the transept during the same century; and if Daniel King's drawing of 1656 is any guide, the tops of the central and western towers had battlemented parapets added during the same period. In any case, it appears that it took much longer to complete the repair of the central tower than that at the south-west. In fact, it is doubtful whether the former was finished until about the end of the thirteenth or the beginning of the fourteenth century, for its fall apparently wrecked much of the vaulting of the transept; and this, from the character of its moulded and carved vaulting ribs in the south arm of the transept, is of the same date as the rose window in the east gable of the presbytery, the rose windows in the east gables of the lady-chapel and the chapels at the east end of the north and south aisles of the choir. This argues that at the end of the thirteenth or the beginning of the fourteenth century, during Bishop Leophardo's episcopate, these works were completed. About the middle of the fifteenth century a stone rood screen was built up between the western piers of the central tower. It thus separated the choir under the crossing from the nave; but through the middle of this screen there was an open archway with iron gates. On either side, as parts of the screen, to the north and south was a chapel, each with its altar. This new work had been known as the Arundel screen, and its erection is often attributed to the bishop of that name, and at the altar in the south side of it Bishop Arundel founded a chantry for himself. Except that the cloister was added and some details of the building altered during the fifteenth century, no other architectural work of any size appears to have been done for many years. [Illustration: DECORATION FORMERLY ON THE CHOIR VAULT. _From an engraving by T. King_, 1814, _lent by the Rev. Prebendary Bennett_. (Scale 7 feet 10-½ in. to 1 in.) (See pp. 42-3.)]