For well over a century after the Norman Conquest of England, an important section of the Anglo-Norman baronage maintained interests and connections in both England and Normandy, and provided a degree of unity between the two countries. In 1204, when King John lost control of the duchy to King Philip II of France, most of these baronial families lost their lands in either England or France, and the old cross-Channel aristocracy of the Anglo-Norman realm was broken apart. In his classic study of the loss of Normandy, Powicke saw the separation of England and Normandy as a significant event that disrupted the extensive ties between the two territories, and propelled both on divergent paths in terms of their political and social development. He believed that many of the important barons of England had been closely connected with the society and culture of northern France, but the separation from Normandy led to a growing national self-consciousness.

Many scholars have subsequently argued that, long before 1204, the aristo-cratic societies of England and Normandy were increasingly going their separate ways, and the cross-Channel interests of the barons were of decreasing significance. Judith Green proposed that social connections created after the conquest became localised very quickly and, by the later twelfth century, true cross-Channel baronial families were very limited in number. David Crouch believed the tendency for families to divide into English and Norman branches, who had a very clear idea of the particular side of the Channel on which their principal interests lay, was an important long-term factor in the collapse of Plantagenet lordship in France. In the view of historians such as Hugh Thomas and Maité Billoré, these developments resulted in a situation by the mid-twelfth century, where most baronial families had become exclusively ‘English’ or ‘Norman’ with most of their interests confined to one side of the Channel. These conclusions suggest the vast majority of barons were indif-ferent to the separation of Normandy and England in 1204. Some historians have highlighted the difficulties in applying such general conclusions to the complex and diverse aristocratic society of the late twelfth century.