The religious orders were the only class who had directly profited by the new regime to increase their power. Hitherto merely national they now became, in a way, part of an international system. Not that they ceased to be patriotic. In the combinations against regal misrule which produced the Great Charters, Bishops and Abbots threw in their lot heartily with the lay barons. But in themselves they formed at this time an almost independent authority with special privileges dangerous to meddle with, because behind them was the Universal Church and its temporal head the Pope, now just reaching the zenith of his authority. It was the religious orders that saved England from barbarism. Each monastery was a kind of impregnable city within which all the graces of civilization were fostered. Here learning, literature and art were diligently studied; rich and poor, bondman and free, were welcomed as scholars if only they proved their ability to profit by the tuition. A certain number of manors were allotted to the Church, and this number was constantly being increased by royal or private benefaction. The tenants of ecclesiastical manors, more especially the villeins or serfs, were in these early times much better treated than those subject to the secular lords. The tenures were generally easy, labour customs could be commuted for a small sum of money, and the serfs could acquire freedom on very moderate terms. Enlightened forms of lease were introduced. The monks were the great agriculturists of the Middle Ages, and so were concerned in the maintenance of facilities for traffic. Apart from this their one duty to the State was to satisfy the _trinoda necessitas_, particularly the care of roads and bridges. This was considered a pious and meritorious duty often rewarded with special indulgences; such undertakings were a work of mercy, in that they befriended the unfortunate traveller. The roads adjoining a monastic estate were usually kept in fair condition, as compared with those in other districts. The first London Bridge was built by the Prior of St. Mary Overie; another great endowed bridge, that over the Medway at Rochester, owes its origin to the great St. Dunstan. Nearly all the picturesque gothic bridges which still survive were the work of the monks. Travelling was in many other ways directly fostered by the monasteries. Communications were constantly passing between the various houses of an order, many of which were on the Continent. Authority for the election of a new abbot or a change in the statutes would have to be obtained from Rome. The two centuries after the Conquest witnessed a continual rebuilding and beautifying of the Abbey Churches. Materials had to be brought from a distance, skilled artists engaged, rich plate, metal work, and ornate vestments procured for the altar-service. All this was a great stimulus to trade.