Richard, King of the Romans and brother of Henry III., is generally credited with raising the Launceston Keep and also the companion one at Restormel. The Keep at Barnard Castle is remarkable for the huge projecting triangular spur, which, springing from the soil, rises to within a few feet of the parapet. The floors were vaulted. This circular Keep is about 50 feet in height and 40 feet wide. Pembroke Keep, on the other hand, rises without buttress or spur or concentric walling straight from a battering base at the ground-level to a height of about 70 feet to the spring of the vaulted roof. It trusted apparently to the enormous thickness of its walls, 20 feet at the base, to defy any attempts at mining. _Conisborough Castle_ possesses the most remarkable Keep of the cylindrical type in the British Isles, both by reason of its extraordinary plan and rare contour. It is a gigantic cylinder nearly 70 feet in diameter, and tapering upwards to a height of over 90 feet. Upon the exterior six enormous buttresses are arranged symmetrically round the face, projecting 9 feet from the surface and being 16 feet wide where they support the cylinder. They diminish in width, however, as they recede from it. These buttresses are carried up the whole height of the Keep, and thus, combined as they are with a massive base of masonry upon which the tower stands, and forming an integral portion of the wall which is about 12 feet thick, we have what is probably the most efficient protection against the deadly mine ever devised as a protection to a British Castle. It may be compared to six enormous spurs, the blowing up of one or even two but little affecting the stability of the remainder. [Illustration: GROUND PLAN OF CONISBOROUGH KEEP.] [Illustration: CONISBOROUGH.] The entrance to the Keep is only a small square aperture placed in the first floor and approached by a long flight of steps in which at one time a drawbridge occurred. The ground floor contains the well and is entered by means of a trap-door in the vaulted ceiling. The buttresses are excavated in places to form chambers, and in one is situated the oratory described by Scott in _Ivanhoe_. It is beautifully vaulted in the Early English style, with carved capitals and bases to the supporting shafts. This grand relic of the feudal period was probably built in the reign of Richard I. by Hamelin Plantagenet, the natural brother of King Henry II., who had married into the de Warrenne family, the rich Earls of Surrey.