The material of the keep is flint rubble, grouted in a copious bath of mortar, and faced inside and out with ashlar. The stones are about 1 foot 6 inches long by 6 inches high, and are a hard and durable variety of chalk, with occasional flints. The material is probably local. The workmanship, though plain and without ornament, is good. The joints are moderately open, enough to admit an ordinary lead-pencil.
The inner ward is something of the shape of the human ear, the keep standing in the west or hollow side, and the lobe being to the north or north-east. This ward measures about 200 feet north and south by 100 feet east and west. Its enceinte wall is one of the curiosities of the castle. It is in girth about 500 feet. Of this the keep, a round tower, and an intermediate building, occupy about one-third on the north-west quarter, and the remaining two-thirds includes some plain wall, a gateway, and seventeen segmental buttresses of 9 feet in the chord, placed upon the curtain 3 feet apart. The wall, about 8 feet thick, is plain within. By means of this arrangement great strength was given to the wall, and a series of flanking defences provided on the only face on which the ground admitted of any attack being directed. This part of the wall was probably about 30 feet high, and stood upon a vertical scarp of about 20 feet more. The battlements are gone, so that it does not appear how the wall was crested. A wall similarly buttressed, and of rather earlier date, existed at the Castle of Cherbourg, and there is something a little like it at Caerphilly.
The keep has already been described. It stands in the line of this enceinte, on the west side, which it protects. Annexed to the keep, on the north side, and also a part of the enceinte, is a rectangular building, probably the lodging of the castellan. It is about 30 feet wide, and 40 feet long, having a basement excavated in the chalk rock. It is of two floors, with fireplaces and segmental arches, and has an appendage on the north, perhaps for offices. It has windows in the curtain looking over the cliff towards the river. Stairs from hence descend to the postern, and the keep stair lies between this building and the keep.
At the northern point outside of, but engaged in, the wall, is the foundation of a round tower, now included in a square bastion, belonging rather to the outer ward than to this.
The postern is common to this and the outer ward, or rather at this point the two run into one, and the postern pierces the common wall. It is a narrow door having a flat top supported by two brackets, and above a round-head arch with closed tympanum. It opens in a re-entering angle of the wall, covered by the bastion, and upon the scarp, so that it must have been reached by a shifting bridge or ladder, the arrangements for working which seem indicated by some recesses for bars just within the portal. There is no portcullis; the defence was a barred door. The cill of this postern is about 30 feet below the base of the keep. It is reached by steps cut in the chalk rock, and but little worn.
The great gateway of this ward opens in the curtain to the east, and had a gatehouse almost entirely within the wall. This gate is considerably below the level of the ward. A steep descent leads to it, and the portal vault has three hanging ribs or arches, with a portcullis inside them, with a square groove. The inner half of the portal is gone; probably there was a second vault and portcullis, and an open space between. The face of the porter’s lodge is gone, but the lodge is seen to have had a plain segmental vault. Outside the gate is a curious square groove as for a portcullis, but it is stopped, and does not descend below the springing level of the gate arch.
This gate opens upon the ditch. The base of the scarp-pier of the bridge remains. The counterscarp has tumbled in. There was, probably, a central pier in the ditch. The present bridge is not original. The approach to this gate left by Cœur-de-Lion was a causeway, formed by leaving the rock uncut. It was over this causeway that the inner ward was stormed and taken.
Just within this gate was a well 270 feet deep, now blocked up.
Outside the enceinte is the ditch, about 20 feet deep, and 30 feet wide at the gate, and along the south front, with vertical sides, but running out to nothing on the steep ground as its ends pass northwards.
This ditch is, in fact, in the outer ward, which envelopes the inner ward. This ward is oblong, about 325 feet north and south, and 200 feet east and west. Its northern half is of an irregular oval form, following the rock, and terminating in two large rectangular conjoined bastions upon the precipitous north end. The southern half is nearly rectangular; having a straight south face 125 feet long, flanked by two drum towers. From these pass off the lateral curtains, forming the east and west front, and ending in two other drum towers, of which that to the east, nearly opposite the inner-ward gateway, is gone. The curtain, from this tower northwards, is also gone. On the opposite or west side it is a mere parapet, cresting the precipice and following its outlines. From the manner in which the inner ward is placed in this ward it occupies nearly all its northern end, but leaves to the south a platform, outside the ditch, of about 140 feet by 100 feet. Here is a rectangular foundation, about 40 feet broad by 60 feet long, and divided lengthways by a wall. Its length is north and south, but here is said to have been the chapel, probably built across one end. It was the work of King John, placed upon a substructure of cellars, and in close contiguity to the castle garderobe in the west wall. “Juxta foricas, quod quidem religioni contrarium videbatur,” says the chronicler. The end walls and the east side are faced with ashlar, but there is now nothing like a chapel. Here, however, it appears to have been, and its roof was visible above the wall. These foundations are interesting, since it was here, through a window in the contiguous wall, that the ward was entered and surprised during the great siege.