By the end of the twelfth century or early in the thirteenth at latest most of England was covered by a network of parishes, each with a centrally located church and generally accepted, if not precisely defined, boundaries. Where there remained a tract of unappropriated land between parishes this was because it was of little value and neither party had felt any great compulsion to claim it as its own. But this was to change. By the end of the Middle Ages such areas had been encroached upon, used for grazing, for felling timber and cutting peat and, above all, for settlement and cultivation. The history of the English landscape is in large measure that of the clearing and reclamation of the forest, marsh and waste. And as land came under some form of profitable use, so it became liable to the payment of tithe to one parish or the other. Most parish boundaries were prescriptive; they had been established at an early date and in many instances had coincided with the limits of some form of secular authority. Indeed, there is abundant evidence that many parishes conformed wholly or in part with the lands of the thegns or lords who had founded and endowed their churches.