A castle, as a not entirely defensive weapon, of considerable potency, could be a threat both to the populace and to its ruler. The king, as warlord and avenger of the law, was inevitably what I have called ‘inspector-general of fortifications’ or he was nothing. Throughout our Middle Ages, the king reserved the right to grant or refuse a ‘licence to crenellate’ to intending castellans. Those who fortified in defiance of this built an adulterine or unlawful stronghold, which would be demolished at once, or at least as soon as the abnormal situation which enabled them to break the law was over.