John Le Patourel, in a classic survey of the governance and administration of the Anglo-Norman regnum, published in 1979, argued that, between 1066 and 1154, Norman practices were introduced into England to a considerable extent, but that this gradually tailed off, more especially after 1154. The ‘Norman Empire’, which collapsed in the 1140s, and its Angevin successor, were two distinct political constructions. The Angevin territorial complex, besides being much the larger, was ruled by a different dynasty, and its distinctive government was based on different principles. In the time of the ‘Norman Empire’, England and Normandy were usually governed jointly by one man. In the short periods when this was not the case, the brothers each had claims on the other's authority. Normally, though, the same authority was exercised in both territories. There was one royal household; one set of household officers; one curia regis, and even one nobility with estates in both countries. Government was effected by the king, constantly on the move with his household. Some adaptations occurred, such as the adoption of the Old English seal and writ, and provision was gradually made for the operation of one judicial system throughout both lands. In Normandy, this Normano-English judicial system provided the forum, and most of the substance, of the Coutume de Normandie. In contrast, Le Patourel argued, the English legal systemwas largely Norman-inspired. The Normans at first tried to take over the organisation of shires and hundreds, and to treat it as they did their Norman comtés, vicomtés and prévôtés, but Heny I saw an advantage in preventing total assimilation. While the shire units remained untouched, as did variations in the conditions of the peasantry, in other areas the process of assimilation continued down to 1135.

During the 1140s, it appeared for several years as though there would be a clean break, until the Angevin dynasty triumphed. From 1154 onwards, the Normanisation of England declined, and the introduction of further innovations in government and administration was much more of a two-way process. However, each segment of the ‘Empire’ had its own Law or Customs, and these were not introduced elsewhere, except to a very limited extent.