The gateway has a slightly four-centred arch, very plain, and set in the usual square-headed shallow recess, intended apparently to receive the platform of the bridge when lifted. There are traces of the chain holes in the spandrels. The whole is placed in a deeper and plain recess, terminating above in a four-centred arch, which carries the parapet, and has behind it three machicolations which protect the entrance. Over the door is the usual portcullis chamber window, and right and left other windows, all small and lancet, some trefoil-headed, and some plain. Two pairs of loops command the approach, one pair has oylet holes at each end of the slit. The other pair have holes, rather larger, at the lower end only. It is the style of loop that marks the introduction of fire-arms. In the jambs of the portal is a half-round portcullis groove, and a little within a pair of folding doors. The entrance passage, 12 feet broad and 30 feet long, is unusually lofty. It is divided by a cross arch into two chambers, both vaulted. The first, 18 feet long, has on the right and left small lancet doors, leading by a narrow vaulted and ribbed mural passage into the lodges, 11 feet by 10 feet. On the left is a second door opening on a circular well-stair, 8 feet diameter, and unusually steep, leading to the upper chambers and roof, and terminating in a turret at the angle of the gatehouse. The vaulting has fallen in, but it is clear that it resembled that of the second chamber. Beneath the cross archway is a second portcullis, and beyond it the second part of the passage. This is 12 feet square, without lateral doorways, and vaulted. The vault is of four cells, three ribs and two half or wall-ribs springing from each corner corbel, and meeting in one central, four lateral, and four half bosses, placed upon two cross or ridge ribs. They are pierced as in the inner ward gate of the Tower of London, and possibly each contained a flower. The openings are, of the central boss 6 inches, and of the others, 4 inches diameter. These apertures can scarcely have been meant for defence; they are too small, and do not command the four corners of the passage. No doubt a long pike might be thrust down some of them, but scarcely, to be of use, down the half holes next the walls. As to pouring down melted lead, pitch, or oil, such articles were always too expensive to form a part of the regular munitions against a siege, nor is there here, nor in portcullis chambers generally, any furnace for heating such materials in any quantity.