Military Architecture in England During the Middle Ages

by A. Hamilton Thompson

CARISBROOKE: steps to keep

The keep of Norman and early Plantagenet days was virtually a castle within a castle. In the mount-and-bailey castle, there was generally only one entrance to the enclosure. If the besiegers forced this and entered the bailey, a ditch divided them from the mount, the most formidable part of the defences. Here the defenders could concentrate themselves for a last struggle, in which the advantage, unless the siege could be prolonged indefinitely, was distinctly on their side. Even where the mount was of inconsiderable height, it commanded the bailey and the ditch at its base. Its sides were too steep to allow of its being climbed without some artificial means of foothold. A chance arrow, tipped with burning tow, might reach the palisade round the summit of the mount, and set it alight in a dry season; but the defending party had all the advantage of being able to discharge their missiles downward and into a large portion of the bailey. Their disadvantage lay in the possibility of a prolonged blockade by a large force, and in consequent scarcity of ammunition and victuals. The danger of fire could be minimised by covering the wooden defences with skins newly flayed or soaked in water; but the work of renewing these in case of a long siege would be difficult.

The wooden donjon on the mount took the form of a square tower surrounded, at the edge of the mount, by a palisade, and approached, as has been described already, by a steep wooden bridge, which crossed the ditch into the bailey. But it is obvious that the existence of a castle in any given place as a permanent centre of royal influence must lead to the abandonment of wooden defences in favour of defences of more lasting material. The stone curtain first took the place of the palisade in the defences of the bailey, and was built across the ditch and up the sides of the mount, ceasing, as can be seen at Berkhampstead ([42]) or Tamworth, at the level of the summit. The next step was to replace the palisade of the mount with a stone wall of circular or polygonal shape. In some instances where this was done, it is possible that the old wooden tower was left within the enclosure. Cases in which a new tower of stone was built upon the mount are rare. Builders would hesitate to charge the surface of the artificial hillock with the concentrated weight of a large square tower. The encircling curtain was much better adapted to the plan of the mount, and distributed its weight more successfully over the edge of the surface. But, with the building of a stone wall round the summit, the necessity of a tower would be removed. Just as, in castles like Exeter and Ludlow, there was from the first a stone wall without a definite keep, the enclosure being virtually a keep in itself, so, in the more limited area of the mount, the encircling wall formed the keep, and, in the larger examples, sheltered upon its inner side buildings, usually of timber, which afforded the necessary cover for the defenders, while their roofs, abutting on the wall below the summit, left room for the rampart-walk and the wooden galleries which were fitted to the curtain in time of siege.

Cardiff; Keep

This was the genesis of the so-called “shell” keep, which converted the summit of the mount into a strong inner ward, the centre of which was clear of buildings, and gave more chance of concentration to the defenders than the narrow passage between the wooden tower and the palisade, into which the angles of the tower would have projected awkwardly. One of the best examples of the type which remains is the keep upon the larger of the two mounts at Lincoln, a polygon of fifteen faces on the outside, twelve on the inside. The wall has lost its parapet, but retains its rampart-walk; it is 8 feet thick, and keeps its height of 20 feet perfect round the whole of the enclosure. The masonry is ashlar of late twelfth century character, and each of the external angles is capped by a flat pilaster buttress. The marks on the inner face of the walls indicate that the enclosure was surrounded by timber buildings, with which two small mural chambers communicated, in the thickness of the outer curtain where it joins the keep. The doorway of the keep is in the north-east face of the wall, which is pierced by a segmental-headed archway, with a semicircular covering arch on the outer face. This doorway, defended by a wooden door with a draw-bar, was approached by a stone stair made in the side of the mount. At the present day the ditch at the foot has been filled up, and the stairs are modern, but originally the ditch must have been crossed by a drawbridge at the foot of the stair, which, when drawn up, would have left the mount isolated from the bailey. There was a small doorway in the south-west face of the keep wall, probably intended to be a postern, through which an exit could be gained in emergencies.[135]

Alnwick; Plan

The shell of masonry upon the mount, however, was by no means the universal form taken by the keep. Sometimes, as at York, the timber defences of the mount survived until a comparatively late period, when their place was taken by a tower of a form in keeping with the principles of fortification of the day.[136] At Alnwick ([115]) the base of the great mount, with a considerable portion of its ditch, remains between the two wards of the castle. The present cluster of towers and connecting buildings upon the mount, surrounding a somewhat dark and confined courtyard, is in large part a nineteenth century reconstruction of the fourteenth century house of the Percys which occupied the site. The outer and inner archways, however, of the gatehouse through which the keep is entered, are twelfth century work, and agree very well in date with the large remains of Norman masonry which can be traced in the curtains of both wards. It is probable that, about the middle of the twelfth century, Eustace, son of John, who died in 1157, surrounded the whole of the present enclosure with stone walls, and, levelling the mount to its present height, built in stone the earliest domestic buildings of the castle, upon the enlarged site of the earlier wooden donjon and palisade. The appearance of Eustace’s buildings must have been very different from that of the mansion of the Percys; and we may assume that he defended the summit of the levelled mound by a thick curtain, against which his hall and other domestic apartments were placed.