This chapter starts by considering the secular (non-monastic) St Peter’s Cathedral, which existed from the seventh century. The evidence is scarce, but by the tenth century it is possible to say that as well as Masses, the clergy were holding a full set of Office Hours (Matins, Lauds, Prime, Terce, Sext, None, Vespers, and Compline). The monastery was founded later in the tenth century, and, by following the scholarship of the American historian and theologian Arnold Klukas, some aspects of the liturgy performed by the monks are considered in relation to the Anglo-Saxon, Romanesque, and Gothic cathedrals in which they worshipped. By this it is sometimes possible to understand both the liturgy and the architecture better. The relationship between these can also be explored through the ‘rubrics’, or performance instructions, that are given in some liturgical manuscripts. The Worcester Antiphoner of c.1230 and an eleventh-century Pontifical are particularly helpful in this regard, and an account of some important ceremonies is given from these, with plans of procession routes around the monastery.