The oldest part of the building to be seen from this point is the strip of walling at the clerestory level. The twelfth-century round-arched windows are there almost complete. In detail they are like those of the tower. Two of them, those in the fourth and fifth bays from the tower, have had later work inserted in the same openings.
The crest of the wall between the west and the central tower was renewed in the fourteenth century. It consists of a parapet with a weathered coping for the top course of stonework, so that the water might not rest upon it and percolate through the walls. Three courses below this is a simply moulded string-course, and immediately beneath is the cusped arcade supported on the course of detached moulded and shaped corbels. For five feet below the bottom of the corbels the newer part of the wall is continued. It will be interesting later to notice the way in which the parapet on the north side of the nave has been dealt with. The reason for the presence of so much new walling at this level is no doubt to be found in the fact that the roof timbers at the time of the second fire were carried down over the walls.
The water from the gutter behind the parapet is carried out on to the backs of the flying-buttresses by means of holes cut through the stonework. Into these pipes are passed which convey the water through to the open gutter channels of the buttresses. The backs of the raking buttresses, though they are sharply weathered to throw the water from them quickly, are also covered with lead as a further protection. These buttresses have carried the thrust of the vaults down-wards with safety for about six hundred years. But the presence of two distinct arches under each of them indicates that they have been altered a little since first they were put up. This was done when it became necessary to carry their thrust farther out because of the new chapels that were added long after the vaults were built over the nave. At the foot of each raking slope is a horizontal piece which runs out until it comes in contact with the octagon pinnacles of the vertical exterior buttresses. It should be noted that where the flying-buttresses meet the vertical wall of the clerestory there is in some cases a portion of the flat buttressing of the twelfth century visible.