The tower occupies the summit of a mound or knoll of earth, in great part artificial, which crowns the steep bank of the adjacent river; rising, perhaps, 60 feet above the stream, and 30 feet or so above the ground to the west of and behind the building. The mound is placed at the apex of an earthwork of rather a pear-shaped outline, of which the river-bank forms the steep east side, while to its base, or north face, has been applied a vallum nearly rectangular, and which may or may not be a Roman addition to a Celtic camp. The mound, which has borne the very considerable weight of the tower in safety, must be of considerably earlier date; and altogether the work resembles much one of those numerous instances in which advantage has been taken of an earlier mound to give elevation to a Norman or early English keep. There are, however, it is said, remains of masonry, of the character and probable age of the tower, still standing upon a part of the vallum, and indications that, as is known to have been the case, the tower did not stand alone, but was within a base court. These walls are not now of any extent, and seem to be included within a modern house built upon the old enclosure. This tower is at its base 37 feet in diameter, and batters inwards to 12 feet high, when it is girt by a bold cordon or string-course, much eroded, but apparently of a half-round section, with a water-groove on its under side. Above this the tower is cylindrical, and 34 feet diameter, or very nearly so, to the summit, which is at present about 60, and may have been 70 feet high. Besides the battering base there is a slight rough set-off, apparently part of the foundation, above ground on the southern face. Round the whole is a walk of about 18 inches broad, so that the mound is about 40 feet across at its top. The tower is composed of a basement and three floors, above which was the battlement, now completely destroyed. The basement within was cylindrical, 18 feet diameter, with walls 9 feet 6 inches thick, and covered by a pointed vault, the ridge of which runs about north-east and south-west. This room was aired rather than lighted by a stepped recess, terminating in a small loop or hole at a considerable height, through which nothing could be seen. It was entered on the opposite or west side by a trap door in the first floor, which lifted within a window recess, and disclosed a flight of eight very steep stairs, 2 feet 7 inches broad, terminating in a doorway rather above 7 feet from the floor; below which, therefore, was probably a wooden ladder. The rebate shows the door to have opened inwards, and to have had bolts on its outer side. The floor is on the level of the top of the mound, and in its centre is a depression which may indicate a well.