Alien priories were religious establishments in England, such as a monastery or convent, which were under the control of another religious house outside of England. Usually the mother-house was located in France.
They were established in England under the first kings of the Norman dynasty, but they soon became settlements of foreign monks, whose sympathies naturally centred in their homes across the seas, and whose main duties were the collecting and guarding of English rents and tithes that were sent year by year out of the kingdom to the parent house.
King John was the first to seize the alien priories, compelling them to pay into the royal treasury the sums or tribute — usually termed apport — which they had been forwarding to the continent. In 1294, when King Edward I of England was at war with France, many of the alien priories were seized, numbering about a hundred, and their revenues were used to help pay for the war. In order to prevent the foreign monks in southern coastal areas giving possible help to invaders, he deported many of them to other religious houses that were twenty or more miles from the coast.
King Edward II of England subsequently followed this example, taking the alien priories into his own hands, but he not infrequently appointed their priors custodians for a consideration, obliging them to pay to the Crown the apport due to their superiors.
When Edward III came to the throne, he restored many of the alien priories to their original owners and waived the arrears of payments due to the Crown. But ten years later, when war broke out again with France, he reverted to the policy of his predecessors, and again seized the property of these French aliens. For twenty-three years, these foreign houses remained in his hands; but with the peace of 1361 most of them were restored, only to be again sequestrated eight years later when the war was renewed. In the time of Richard II, the alien priories continued mostly in the hands of the Crown.
In 1378, all the monks in alien priories were expelled from England.
They finally came to an end under Henry V in 1414. Those that had not been already assigned with the Pope's assent to other religious purposes, were finally suppressed by the Parliament of Leicester, and their revenues taken into the king's hands. The Crown, however, in most cases transferred the property to other monasteries.
- Coredon Dictionary of Medieval Terms p. 10