Most of the peasantry were bonded to their masters. Serfs, cottars or slaves, who may have composed as much as 88 per cent of the population in 1086, were bound by law to work on the land. They could not leave without permission of their Lords. But also, even those who were classed as free men were factually limited in their freedom, by the limited chances to acquire property. The Commons Act 1236 allowed the Lord of a Manor to enclose any manorial land that had previously been common, and the Statute of Westminster 1285 formalised the system of entail so that land would only pass to the heirs of a landlord. The Statute "Quia Emptores Terrarum" 1290 allowed alienation of land only by substitution of the title holder, halting creation of further sub-tenants. The civil liberties of the Magna Carta of 1215, and its reissue in 1297, were only meant for barons and lords, while the vast majority of people were poor, subjugated and dispossessed. Feudalism had not always been a part of English society, rather than being positively imposed by the monarchs prior to the Norman Invasion. However, from 1348 everything changed as the Black Death swept through Europe, killing a third of the population. People like the poet Geoffrey Chaucer had seen subservience as part of a natural social order, ordained by God. But if landowners had themselves survived the plague, the peasants' labour on the land had become very scarce. Ironically, the surviving peasants were in a greater position of economic power, in claims or bargaining for wages. Feudalism began to break down. First, serfs could undergo "commutation", where the lord simply agreed to accept money rents from tenants instead of labour services. This did not mean freedom itself, but abandoning forced labour and payments in kind to landlords meant the open evidence of servility was concealed. In disputes, royal courts were increasingly biased toward declaring a peasant was free. Second, through an act of manumission lords could voluntarily grant freedom and this was increasingly done, after the plague, if the serf or a relative made a payment of money. Third, the common law stated that if a serf lived on free soil, as in a chartered town or Royal demesne land, for a year and a day, they would become free. The nobility and the King reacted to the rising bargaining power of the peasantry by fixing wages, and violently suppressing any uprisings, like the Peasants' Revolt in 1381.