It is reached by a dimly-lit, impressive passage, which is entered from the north choir aisle through a doorway with deeply-sunk mouldings and carved capitals. Two heads, slanting inwards in a rather awkward manner, support the curious pediment-shaped canopy over the doorway. At the commencement of this fine passage, just within the doorway, is a small vault supported on extremely odd corbels, as if the mason had taken advantage of the obscurity to wanton with his craft. One is a large head with enormous cheeks, apparently suffering from acute neuralgia; a handkerchief, under which a few comically-stiff curls escape, covers the head and is tied under the chin; another represents two dragons biting each other, with a head upside down beneath them; another, which reminds one of the worst eccentricities of modern crockery, is formed by a hand holding a foliated capital. I suppose that the head with swollen cheeks is really another testimony to St. William Bytton's power over the toothache. The undercroft itself was finished before 1286, perhaps some time before; but the more advanced sculpture of the passage looks as if that part were built in the "toothache" period--that is to say, some ten years or so after Bytton's death in 1274. [Illustration: Chapter-House--Undercroft.] Certainly the bosses of the vault in the passage beyond the doorway are of a character that suggests the transition to Decorated which was in progress at this time. They are elaborate, and, with one exception, through-carved. The first from the door represents a head, the next an _Agnus Dei_, the next two grotesque heads joined together, then apparently the Serpent tempting Eve, then an ox, dragons, two small grinning heads, with animals apparently biting them on one side. The corbels are carved into heads, some crowned, others reversed with the shaft in their mouths. On the right-hand side, as one enters the undercroft, a pretty stone lantern projects from the wall; of the little mullions which form its face, one is set far enough from the wall to admit of the insertion of a lamp. Two heavy wooden doors at the entrance leave no doubt as to the purpose for which the undercroft was built. The outer door is the most massive; it is studded with nails, and has two great bolts and a huge lock: on the outer side a kind of escutcheon is formed round the keyhole by a heart-shaped piece of iron, surmounted by a cross; on the same side there is an iron bar, and the hook to hold it across the doorway. A deep hole has been worn in the pavement by the feet of those who pulled open the door. The inner door is lighter, and ornamented with beautiful elaborate hinges: on this side are deep sockets in the wall, into which the inner bars were run.