About 1450 the south-east corner of the central tower gave way, and so unsafe was the church that service had to be held in the Lady-kirk. In consequence of this disaster the Canons were obliged to rebuild not only the south and east sides of the tower, but also the east side of the south transept, and eventually part of the south side of the Choir; and it is evident that they would have rebuilt the two remaining sides of the tower, had they not been prevented by the Dissolution. The present rood screen and canopied stalls were put in toward the close of the fifteenth century. In 1502 the Lady-kirk (in which a chantry had been founded in 1392) was handed over by the Chapter to Archbishop Savage, who in turn transferred it to Fountains Abbey. Abbot Huby, intending to make it a colony of Cistercians, rebuilt the east end of it, and enclosed part of its graveyard with a fine stone wall having a strongly-marked base. Of this wall a great part remains in St. Mary-gate. A large doorway in it has been built up. The Lady-kirk itself has vanished long ago. At this time was begun the greatest architectural enterprise that had been undertaken at Ripon since the twelfth century, namely, the rebuilding of the nave of the minster. The Transitional nave, it was said, had become ruinous through age and storms, but the real motive for its destruction was probably an ambition to enlarge the building. The enlargement of aisleless churches was usually begun by the addition of a single aisle, and that on the north side (since the south was usually the side of the graveyard); but at Ripon the south aisle was built first, perhaps because it was always intended that there should be two aisles--an arrangement which there were no cloisters here to prevent. The work was begun in 1502 or 1503. Delayed by a plague in 1506, it was almost complete, as Leland's _Itinerary_ shows,[21] when he visited the town about 1538, but the aisles had not yet been vaulted when the Dissolution came, and had wooden roofs until our own time. Irreparable as is the loss of Archbishop Roger's nave, its successor must surely be placed among the great naves of the Perpendicular period--and it is the latest of them. The work was furthered by =Archbishop Savage= (1501-1507) and by =Cardinal Archbishop Bainbridge= (1508-1514), and two canons must especially be mentioned in connection with it, Andrew Newman, appointed Master of the Fabric in 1502, and =Marmaduke Bradley=, who was paymaster, and who was connected with the repairs after the failure of the central tower, and gave up to the fabric a large portion of his fees for residence. The last work done before the Reformation was probably the rebuilding of the three westernmost bays on the south side of the choir, which had been weakened doubtless by the accident to the central tower.