From the establishment of the first Norman bishop in 1067, the holder of the Durham bishopric with its massive estates, was expected to act vigorously on the king's behalf to counter vestiges of northern particularism and threats of Scottish invasion.
Successive bishops strengthened their own position, most notably by the separation of Durham from the Earldom of Northumberland, to form a separate county, by appointing their own sheriffs in Durham and Norham, answerable to the episcopal and not the royal Exchequer.
The administration of justice in the franchise was largely in the hands of the bishop. By the early thirteenth century, his jurisdiction in criminal matters, including pleas of the crown, was fully established, and it was already asserted that it was the bishop's and not the king's peace which was at stake. In civil pleas, the bishop's courts were less independent.
1293 marked a turning point in the definition of the franchise. In addition to the first assertion of palatine status, the year saw a successful defence by Bishop Bek, in the course of royal quo warranto proceedings, of his prescriptive right to a regalian franchise and of Durham's independence of the sheriff of Northumberland.
The application of the term palatinate gave a sense of homogeneity to the somewhat miscellaneous collection of regalian and lesser franchisal rights. Although in practice the small scale of the Palatinate placed some restrictions on institutional development, in theory it reproduced the kingdom in microcosm. At its head was the bishop with his council. His Chancery, headed by the temporal Chancellor who held the great seal of the Palatinate, performed both administrative and judicial functions.
The Exchequer was responsible for the collection of all the bishop's revenues, including those from his vast estates. The courts of the Palatinate, staffed by the bishop's justices, maintained the bishop's peace and heard pleas on writs issued by the Chancery in the bishop's name.
The major developments in the Palatinate in the later Middle Ages were in the administration of justice. Many of these reflected changes in the realm at large. The bishop's civil jurisdiction was gradually extended, by a gradual process of unchallenged encroachment, the palatine courts came to offer suitors all writs available at Westminster.
In theory, the later medieval Palatinate was almost entirely separate from the judicial system of the kingdom. The inhabitants were supposed to plead only in the palatine courts, with final appeal to the bishop. Only an allegation of defective episcopal justice enabled a plaintiff to undertake proceedings in the Westminster courts on a writ of error. In practice, however, it is likely that, as in earlier and later centuries, this isolation was not watertight.
The Palatinate functioned also at county level. The bishop's sheriffs of Durham and Norham performed standard shrieval duties: judicial, financial, police and occasionally military. The sheriff for the time being was normally the bishop's escheator, with responsibility for matters arising from feudal relations, and particularly for holding inquisitions post mortem. Coroners existed in the franchise before 1279; the bishop appointed coroners for each of the four wards of Durham and for Sadberge.
A Marshalsea Court was held in the Palatinate from the fourteenth to the sixteenth century. As lord of a regalian franchise, the bishop of Durham also enjoyed during the Middle Ages rights which formed the basis of later admiralty jurisdiction.
Technically, the management of the bishop's estates and his relations with his tenants thereon, free and unfree, were distinct from his palatine administration. This distinction, however, could never be observed rigidly. First, it was the income from his vast estates, and not the profits of palatine lordship, which made the bishop of Durham one of the wealthiest of English prelates. Secondly, at any time the same man might be appointed by the bishop to key offices in both palatine and estate administration. Thirdly, the overarching authority of the bishop's Exchequer in matters financial tended to blur the distinction between the two sides. In judicial matters, the bishop's Halmote Court dealt with copyhold tenants.
Durham, in common with the other palatinates, was affected by the 1535 Act for the Recontinuation of Liberties and Franchises, which came into force on 1 July 1536. This brought important changes to the Palatinate's status: pardons for felonies and outlawries, and the creation of justices in eyre, of the peace, and of assize and gaol delivery were henceforth reserved to the monarch alone; all writs and indictments were to be in the king's name; and the king's peace was to replace the bishop's peace.
Nevertheless, the functioning of the palatine courts remained almost untouched, co-ordinated with but still outside the national judicial system. Moreover, other aspects of the Palatinate were unaltered: the bishop continued to appoint sheriffs, coroners and other officers and maintained his financial administration, until 1836.
In the sixteenth century and probably later, the palatine courts did not enjoy exclusive jurisdiction, at common law or in equity, over inhabitants of or property within the Palatinate. Durham first came under the jurisdiction of the Council of the North in 1537.
In 1553, efforts by the Lord Protector to abolish the Palatinate, failed with the death of King Edward VI. Thereafter, the palatine administration remained untouched in essentials until the 1640s; after the outbreak of the Civil War in 1642 the palatine judiciary ceased to function, and the Palatinate itself was abolished by Parliament in 1646. An Act of 1654 placed Durham on the same footing as all other counties. After the Restoration, however, the pre-war situation was restored almost in its entirety, save for the disappearance of feudal tenures and incidents, as in the kingdom as a whole.
Parliamentary representation for the county and city was provided for the first time (except during the Commonwealth) by an Act of 1673. A suggestion for the abolition of the Palatinate was made in 1688, but it was abandoned in the face of local concern at the possible loss of the allegedly useful Durham courts. Thereafter, little changed until the nineteenth century.
In the 1830s, the movements for reform of the Church of England and of the legal system combined to bring about the end of the Palatinate of Durham. A bill was introduced in the House of Lords in 1836 proposing, in effect, the abolition of the Palatinate and all the Durham courts, and the absorption of Durham into the national administrative and judicial framework. The Act which was finally passed was less sweeping: it separated the bishop's ecclesiastical and temporal powers and provided for the vesting of all palatine rights in the Crown, as a distinct franchise. Of the local courts, only the county court was abolished.
Of the remaining local courts, the Court of Pleas was abolished by the Judicature Act of 1873, which also ended Durham's separate assize commission and provided for the absorption of the Palatinate into the newly-formed north eastern assize circuit from 1876. The Durham Chancery Court continued to function until merged with the High Court of Justice by the Courts Act of 1971.
In other respects, the county of Durham from 1836 was no different from other English counties. Geographically, it was gradually subjected to the nineteenth-century process of rationalisation.