Under Count Philip of Alsace, Flanders had become one of the mightiest and most progressive principalities of western Europe. In 1191, the power relations between Flanders and France had been reversed: the king now constantly undermined the counts' power. The highest governmental organ, the count's curia, showed a clear tendency towards professionalisation. Since the first half of the eleventh century, the county of Flanders had been subdivided into castellanies, chatellenies, districts under the control of the viscounts residing in a central borough. The Flemish nobility was primarily determined by birth; free status, vassalage, the ownership of allodia and the possession of seigneurial rights were further but not essential characteristics. The continuous population growth increased pressure on the land as a response to the high demand for agrarian products. The intensive use of the land is only one aspect of the highly developed Flemish economy. After northern Italy, Flanders was the earliest and most densely urbanised area of medieval Europe.