The arcade against the north wall is continued in the vestry, and it has been thought that it is Norman, and that its arches were once open.[110] But had this ever been the case the piers would surely have been narrower, and would have had capitals. Indeed, it is doubtful whether the arcade is Norman at all: for if it were, its bays might be expected to agree in span and number with the (presumably Norman) bays of the crypt, whereas there are five bays there and only four here occupying the same total length. Secondly, the set-off on which its piers stand is probably Archbishop Roger's work, as will appear later; and the piers themselves seem to be of the same construction with the wall behind them, which again is almost certainly his. Moreover, it is significant that the arches agree in span with those of his choir, and that their piers are back to back with his vaulting-shafts in the choir-aisle. Lastly, these piers correspond in width with his buttresses on the north side of the choir. In fact it is difficult to resist the conclusion that they are Archbishop Roger's south choir buttresses in disguise,[111] and that the arches between them were thrown across merely to form a straight boundary for the vaulting, and to carry a ledge which (when there was no storey above) might support the external roof. The piers indeed are carried up, with a 'straight joint' on either side, above the springing of the arches, and the latter are constructed as if they had been let into the piers as an after-thought.[112] As the bays of this arcade, to which the vaulting is adapted, do not agree with those of the crypt, it follows that the two cylindrical pillars here do not stand exactly over the pillars below--which strengthens the presumption that the vaulting there is of earlier date, and that its groin-ribs were added later for strength: nor does the dividing wall here stand exactly over the cross-wall below, so that the strain on the crypt roof must be considerable.