In The Pillars of the Earth, Prior Philip's duty is to keep the priory running smoothly and if possible, at a profit, while balancing his spiritual commitment with his drive to see the village prosper. The market and fleece fair are part of his plan; the cathedral to attract pilgrims is another. The monks of Kingsbridge may have left the world, but they still have to interact with it, and that includes not paying more for food than necessary. Those duties also involve both church and real-world politics, knowing how to deal with powerful, dangerous people like Waleran, the Hamleighs and King Stephen. Even then, Philip gets a few nasty surprises: Waleran's attempt to have land transferred to his diocese and for his personal use, the Hamleigh's acquisition of the quarry, risk of the king's disapproval if work isn't proceeding fast enough.
Waleran Bigod is just as devout as Philip, but his devotion is to a political version of the Church rather than to the Divinity behind it. He's willing to use people like the Hamleighs for his own ends, he'll sanction murder, and even commit it himself, once he's convinced the act is justified. The old Bishop of Kingsbridge died from poison, just as Alfred Builder did and Jack Shareburg was meant to, and Waleran might even have been behind the convenient death of King Henry. He shows sincerity to his warped interpretation of God by harming himself, with whips and nails and spiked belts; but since man's body is supposed to be in God's image, it's a back-handed compliment at best. Waleran's question would not be "Why build a cathedral?" but "Why build one here?" Though Kingsbridge has grown in wealth and status, the logical place for a cathedral to his mind, and certainly to the Hamleighs, would be Shiring, where wealth and status already exist. If Kingsbridge cathedral became sufficiently imposing, Waleran might find himself trapped there, in a backwater away from the centre of power. For an ambitious high churchman, that would never do.
Philip's immediate subordinate is sub-prior, Brother Remigius, a sly monk with ulterior motives and who is under the strong thumb of Waleran Bigod. A sub-prior carries out the prior's duties in his absence or illness, and replaces him in the event of his death unless the monks elect someone else. Remigius becomes bitter and vengeful when he sees Philip elected Prior. His increasing difficulty balancing his work as a monk and his job as Waleran's eyes and ears drive him to desperate acts.
Brother Cuthbert's role in Kingsbridge