This volume presents a kind of anticipated companion volume to the HBS edition of the Directorium Sacerdotum, a variety of ordinal or directory, which was privately compiled by Clement Maydeston, who though a priest held formally the post of "deacon" at the Brigittine Abbey of Syon, Middlesex (c. 1390-1456). Despite these origins, the compilation acquired a de facto official status. The Directorium Sacerdotum itself was published as volumes 20 and 22.
The Directorium aimed in part at providing calendrical and rubrical solutions for those observing the Sarum Use. It did this by making a distinction between the practice of the Salisbury cathedral chapter and the practice that could reasonably be required from the many others in England who followed in general the Sarum Use. Maydeston's position was that outside the Salisbury chapter it was reasonable to make modifications to meet local conditions and calendars. This was deemed unacceptable by some, who maintained that the practice observed at Salisbury itself should be followed everywhere. This line of argument ignored the fact that in any case there were contradictions between the existing manuscript drafts of the Sarum ordinal and the rubrics of the liturgical books.
The edition focuses in particular on two printed texts which offer Maydeston's defence. The first is the Defensorium Directorii Sacerdotum printed in successive editions of the Directorium Sacerdotum by Wynkyn de Worde in 1495. The second is the text Crede Michi, a longer and more considered rubrical tract compiled by Maydeston but incorporating rubrical adjudications made by the Salisbury canons c. 1440-1450, and partly based on an earlier work by one John Raynton. The text given is that printed by Wynkyn de Worde in the quarto of 1495.