William fitzHerbert's early career has received little attention. Archdeacons and canons were seldom considered worthy of individual mention in contemporary accounts of ecclesiastical affairs. It was not until the election dispute propelled William onto the international arena that he came to prominence in twelfth-century chronicles, and modern historians, understandably enough, have focused almost exclusively on the bitter and long-drawn-out controversies which surrounded his election to the archiepiscopate. However, the three decades which he spent as treasurer of York Minster and archdeacon of the East Riding, though sparsely documented, are by no means as obscure as has been supposed. Nor are they lacking in controversies, incidents and dramas replete with interest in their own right. But there is more than that: these years constitute not merely a prelude to, but also a means to understanding William's final, controversial period as arch-bishop. Many of the issues and personalities which were so prominent during his archiepiscopate had already appeared, in one guise or another, at earlier stages in his life. A study of William the treasurer is an essential introduction to William the archbishop.

The office of treasurer of York Minster was established by the first Norman archbishop, Thomas of Bayeux (1070–1100). In the years around 1090 he reorganised the Minster clergy and instituted the dean and chapter as the corporate body responsible for the running of the cathedral. The constitution (if it is not anachronistic to talk in such precise terms) was similar to that established at other secular cathedrals at about the same time. Along with the dean, the precentor and the master of the schools (later known as the chancellor), the treasurer was one of the four dignitaries of the Minster. All four had certainly come into existence by 1093, and Ranulph, the first treasurer, possibly occurs as early as 1091. Thomas of Bayeux also introduced archdeacons to the diocese of York. The archdeacons were not members of the cathedral chapter ex officio, but it was customary for them to hold one of the Minster prebends, and this gave them a seat in chapter. The archdeaconry of the East Riding, uniquely, was held in tandem with the office of Minster treasurer. Thus Ranulph the treasurer was also archdeacon of the East Riding, as were William fitzHerbert and all of his successors as treasurer down to 1218, when Archbishop Walter de Gray separated the two offices.