Note the plural! Once upon a time, only one prayer book was used throughout the Church of England and its use was compulsory. Fundamentally, it was the work of Archbishop Cranmer at the time of the Reformation, and was notable for its protestant theological basis, not only in the actual liturgy itself, but also in the rubrics (instructions to the officiant). Early in the twentieth century, steps were begun to modernise its language in order to make it more acceptable to the worshipper of that time. A revised prayer book (which, it must be said, as well as modernising the language moved back to pre-reformation theology) was drafted and put before Parliament for approval (before the advent of synodical government any changes in the doctrine and practices within the Church of England had to be approved by Parliament in order to become effective). The new prayer book (known as the 1928 prayer book) was, after heated debates, turned down and the possibility of modernisation had to wait another three decades. It became practicable with the establishment of synodical government, first in a series of so-called experimental services authorised for a specific period. These, after trial and amendment, were collected in the Alternative Service Book of 1980, now superseded, after further substantial liturgical revision, by Common Worship published in 2000. The Book of Common Prayer remains a defining document in the theology of the Church of England.