In medieval and Early Modern England, Wales and Ireland, a deer park (novale cervorum, campus cervorum) was an enclosed area containing deer. It was bounded by a ditch and bank with a wooden park pale on top of the bank, or by a stone or brick wall. The ditch was on the inside increasing the effective height. Some parks had deer "leaps", where there was an external ramp and the inner ditch was constructed on a grander scale, thus allowing deer to enter the park but preventing them from leaving. Some deer parks were established in the Anglo-Saxon era and are mentioned in Anglo-Saxon Charters; these were often called hays (from Old English heġe (“hedge, fence”) and ġehæġ (“an enclosed piece of land”). After the Norman conquest of England in 1066 William the Conqueror seized existing game reserves. Deer parks flourished and proliferated under the Normans, forming a forerunner of the deer parks that became popular among England's landed gentry. The Domesday Book of 1086 records thirty-six of them. Initially the Norman kings maintained an exclusive right to keep and hunt deer and established forest law for this purpose. In due course they also allowed members of the nobility and senior clergy to maintain deer parks. At their peak at the turn of the 14th century, deer parks may have covered 2% of the land area of England. After the Norman conquest of Ireland in 1169 many deer parks were established in the new Lordship of Ireland. The fallow deer is not native to Ireland and is believed to have been introduced at the royal deer park at Glencree in 1244. The Cambro-Norman landlords also used deer parks to produce timber and charcoal, and to protect their livestock (cattle, sheep, etc.) from being stolen by the native Gaelic Irish. Research by Fiona Beglane identified forty-six Irish deer parks established before 1400. James I was an enthusiast for hunting but it became less fashionable and popular after the Civil War. The number of deer parks then declined, contemporary books documenting other more profitable uses for such an estate.