How far was there an administrative policy peculiar to Norman rule in Normandy, England, southern Italy and Sicily and Antioch, the crusading kingdom established in the early twelfth century? In 1969, D.C. Douglas stated the case as follows:
“Before the twelfth century was far advanced, monarchies established by the Normans controlled the best organised kingdoms in Europe and a Norman prince ruled the strongest of the Crusading states. This success was, however, not due merely to the facts of conquest or even to the establishment of notable rulers supported by strong feudal aristocracies. It derived from a particular administrative policy which was everywhere adopted by the Normans. In all the states they governed, the Normans at this time were concerned to give fresh vitality to the administrative institutions that they found in the conquered lands and to develop these constructively to their own advantage.”
In Sicily, as in England, historians have implied that the Norman rulers chose the best practices and institutions and incorporated them into the Norman system that their 'genius of adaptation' then developed into one that was more efficient and more successful than its predecessor.
The claims made by Douglas and his predecessors have been strongly challenged for England by James Campbell and W. L. Warren. They suggest that the evidence for Anglo-Norman administration is open to a fundamentally different interpretation. Warren attacked the ‘myth of Norman administrative efficiency’:
“Until the end of the eleventh century, Anglo-Norman England was largely managed by Englishmen. The crisis in continuity emerges not at the Conquest but as the generation personally familiar with pre-Conquest practice dies off and the Normans had to cope for themselves. The critical questions are how far were they able to master the Anglo-Saxon inheritance and how far they understood it. The innovations in administrative practices were...at least in part a response to problems which the Normans themselves inadvertently created and an attempt not so much to improve upon the Anglo-Saxon system as to shore it up and stop it collapsing...Under the Normans, the Anglo-Saxon system became ramshackle. Norman government was a matter of shifts and contrivances. Nevertheless, there is a break in continuity, not at the Conquest itself...but within fifty years. The break occurred not because the Normans did not wish to preserve the Anglo-Saxon inheritance but because they did not know how to...”
What is now clear is that. First, in the immediate post-conquest period, in England and Sicily, the Norman rulers sought to adapt native administrative practices to their own needs. Secondly, in both areas a generation after the conquest, there was a break in continuity caused by a failure of the conquerors to preserve the administrative structure inherited from the previous rulers. Finally, in Sicily, as in England, Norman rulers then introduced administrative innovations to repair the damage done to the pre-conquest system; innovations that underwent rigorous selection through a process of trial and error and rapidly developed in new directions.
There were, however, important differences between the ways in which the Norman rulers of England and Sicily adapted native administrative processes to their own needs. In England, the Norman rulers initially perpetuated the Anglo-Saxon inheritance by employing native administrators. Until 1071, a significant group of English earls and thegns retained power and status and played a significant role in the post-conquest settlement. After 1071, at the level of the shire a small but vital administrative community of Anglo-Saxons survived ensuring the continuity of Anglo-Saxon customs and traditions. After the conquest of Sicily was completed in 1091, no Muslim lords held land in fief from the Normans. Although Sicilian Arabs must have been employed within the early Norman administration, we know the name of only one before 1130 while an entire class of Greek Christian administrators was imported from east Sicily and Calabria to manage and adapt the Arab and Islamic institutions through which the island was administered.
Linguistically, there were parallels between England and Sicily. Both islands had become 'trilingual' as a result of the conquest though it is important to recognise that a concentration on three big languages oversimplifies the complex linguistic structure of the islands. For example, it ignores the linguistic diversity of north and west Britain and the wide variation of Romance vernaculars in the Sicilian kingdom. It also neglects the Scandinavian communities in Britain and the presence of some Normans who still had Norse personal names. In England, although Old English (Anglo-Saxon) was the administrative language before 1066, Latin was already the dominant literary language and soon after the conquest (around 1069) replaced Old English as the language of records, though it retained the unwritten language of local government. French (Anglo-Norman) was introduced after 1066 as the language of the victorious elite, but, except in the king’s court, French-speakers were soon assimilated into English-speaking society. French was soon established as a literary language but it was not until the mid-13th century that it was widely used as a language of record.
In pre-conquest Sicily, Arabic was the dominant language of administrative at all levels, of literary culture and of religion. Greek was confined to monasteries and to the Greek urban societies of eastern Sicily. Even the non-Muslim minorities (Jews and Greek Christians) seem to have been predominantly Arabic-speaking. After the conquest, Arabic continued to be used in some documents for a generation but was then dropped. Greek was established as the language through which the Normans ruled and rapidly became the dominant language of administration on the island. By 1110-15, the almost complete replacement of Arabic by Greek and of Arab Muslim by Greek Christians in the central administration hastened the collapse of the pre-conquest administrative system far more than the, as yet, insignificant introduction of Latin. The new Greek structure incorporated some things salvaged from the pre-conquest Muslim administration but it was essentially new and foreign. Latin lords and their Arab 'villeins' used, respectively Latin (or a Romance vernacular) and Arabic with Greek Christians acting as intermediaries between the two communities. In post-conquest England, an educated person might read and write Old English, Latin and French but in Sicily, such ‘trilinguism’ was uncommon and confined largely to the Greek Christian community. In the long term, the language of the Norman conquerors enriched English but was replaced by it as English became the dominant language throughout Britain. In Sicily, the Romance vernaculars of the Normans had almost completely ousted Arabic by the end of the 13th century and medieval Sicilian contained only some three hundred words of Arabic derivation.
The Anglo-Saxon and Muslim inheritances were fundamentally different from each other and the Norman rulers sought to adapt these inheritances in England and Sicily in very different ways. This contrast is reinforced by the ways in which Henry I and Roger II each sought to make good the damage done to the pre-conquest systems. In England, Henry I replaced existing Anglo-Saxon social mechanisms with a series of innovations amounting to a rapid expansion of the early state and the administrative machinery through which it was governed. Roger II sought to preserve and to restore the system inherited from Muslim Sicily by importing administrative practices, institutions and personnel wholesale from the contemporary Muslim world so that the Arabic administrative of Sicily in the mid-12th century resembled the classical Islamic system as exemplified by contemporary Fatimid Egypt. In England, the existing Anglo-Saxon system was close to collapse. Henry I had little choice but to innovate. In Sicily, Roger II sought to repair the existing native system and gave a new lease of life to previously decaying Arabic and Islamic administrative systems and institutions. At the same time, Roger II and his successors introduced a series of far-reaching innovations in the Greek and, especially in the Latin branches of the administration.
There are important differences in the ways in which the Normans in England and Sicily responded to a common problem: how should they react to the collapse of existing native institutions? ‘Administrative efficiency’ was not the consequence of the conquests but a necessary response to Norman failure to maintain the administrative systems they inherited. Good governance had to be created in England after 1100 and recreated in Sicily after 1120. This was the administrative achievement of the Normans.
 D.C. Douglas The Norman Achievement 1050-1100, Eyre & Spottiswoode, 1969, pages 181-182. Douglas was here following the view expressed by C. H. Haskins in his ‘England and Sicily in the twelfth century’, English Historical Review, volume 103, (1911), especially pages 433-5 where he stressed that a ‘genius for adaptation’ characterised Norman government in Normandy, England, Italy and Antioch.
 James Campbell ‘Observations on English government from the tenth to the twelfth century’, Transactions of the Royal Historical Society, 5th series, volume 25, (1975), pages 39-54 and W. L. Warren ‘The myth of Norman administrative efficiency’, Transactions of the Royal Historical Society, 5th series, volume 34, (1984), pages 113-132.