See M. Gibson, Lanfranc of Bec (1978).
Lanfranc was trained in the liberal arts, at that time a field in which northern Italy was famous. (There is little or no evidence to support the myth that his education included much in the way of Civil Law, and none that links him with Irnerius of Bologna as a pioneer in the renaissance of its study.) For unknown reasons at an uncertain date, he crossed the Alps, soon taking up the role of teacher in France and eventually in Normandy. About 1039 he became the master of the cathedral school at Avranches, where he taught for three years with conspicuous success. But in 1042 he embraced the monastic profession in the newly founded Bec Abbey. Until 1045 he lived at Bec in absolute seclusion.
To his influence we may attribute the desertion of Berengar's cause by Hildebrand and the more broad-minded of the cardinals. Our knowledge of Lanfranc's polemics is chiefly derived from the tract De corpore et sanguine Domini, which he wrote many years later (after 1079), when Berengar had been finally condemned. Though betraying no signs of metaphysical ability, his work was regarded as conclusive and became for a while a text-book in the schools. It is often said to be the place where the Aristotelian distinction between substance and accidence was first applied to explain Eucharistic change. It is the most important of the surviving works attributed to Lanfranc; which, considering his reputation, are slight and disappointing.
Henceforward Lanfranc exercised a perceptible influence on his master's policy. William adopted the Cluniac programme of ecclesiastical reform, and obtained the support of Rome for his English expedition by assuming the attitude of a crusader against schism and corruption. It was Alexander II, possibly a pupil of Lanfranc's and certainly a close friend, who gave the Norman Conquest the papal benediction--a notable advantage to William at the moment, but subsequently the cause of serious embarrassments.
Lanfranc, during a visit which he paid the pope for the purpose of receiving his pallium, obtained an order from Alexander that the disputed points should be settled by a council of the English Church. This was held at Winchester in 1072. At this council Lanfranc obtained the confirmation of primacy that he sought; nonetheless he was never able to secure its formal confirmation by the papacy, possibly as a result of the succession of Gregory VII to the papal throne in 1073.
Lanfranc assisted William in maintaining the independence of the English Church; and appears at one time to have favoured the idea of maintaining a neutral attitude on the subject of the quarrels between papacy and empire. In the domestic affairs of England the archbishop showed more spiritual zeal. His grand aim was to extricate the Church from the fetters of corruption. He was a generous patron of monasticism. He endeavoured to enforce celibacy upon the secular clergy.
He obtained the king's permission to deal with the affairs of the Church in synods. In the cases of Odo of Bayeux (1082) (see Trial of Penenden Heath) and of William of St Calais, bishop of Durham (1088), he used his legal ingenuity to justify the trial of bishops before a lay tribunal.
He accelerated the process of substituting Normans for Englishmen in all preferments of importance; and although his nominees were usually respectable, it cannot be said that all of them were better than the men whom they superseded. For this admixture of secular with spiritual aims there was considerable excuse. By long tradition the primate was entitled to a leading position in the king’s councils; and the interests of the Church demanded that Lanfranc should use his power in a manner not displeasing to the king. On several occasions when William I was absent from England Lanfranc acted as his vicegerents.
Lanfranc's greatest political service to the Conqueror was rendered in 1075, when he detected and foiled the conspiracy which had been formed by the earls of Norfolk and Hereford. Waltheof, 1st Earl of Northumberland, one of the rebels, soon lost heart and confessed the conspiracy to Lanfranc, who urged Earl Roger to return to his allegiance, and finally excommunicated him and his adherents. He interceded for Waltheof’s life and to the last spoke of the earl as an innocent sufferer for the crimes of others; he lived on terms of friendship with Bishop Wulfstan of Worcester.
On the death of the Conqueror (1087) he secured the succession for William Rufus, in spite of the discontent of the Anglo-Norman baronage; and in 1088 his exhortations induced the English militia to fight on the side of the new sovereign against Odo of Bayeux and the other partisans of Duke Robert. He exacted promises of just government from Rufus, and was not afraid to remonstrate when the promises were disregarded. So long as he lived he was a check upon the worst propensities of the king’s administration. But his restraining hand was too soon removed. In 1089 he was stricken with fever and he died on May 24 amidst universal lamentations. Notwithstanding some obvious moral and intellectual defects, he was the most eminent and the most disinterested of those who had co-operated with William I in riveting Norman rule upon the English Church and people. As a statesman he did something to uphold the traditional ideal of his office; as a primate he elevated the standards of clerical discipline and education. Conceived in the spirit of popes such as Leo IX, his reforms led by a natural sequence to strained relations between Church and State; the equilibrium which he established was unstable, and depended too much upon his personal influence with the Conqueror.