Textual study indicates that Robert de Boron wrote in prose, and is the author only of the Joseph part of the cycle associated with him.

The standard intimation in guides to Arthurian literature is that Robert de Boron composed a verse Joseph and Merlin of which only a single manuscript survives; that the Merlin is fragmentary, but that we know what it contained because we have a prose redaction of both works made not long afterwards. I have already endeavoured to show that this hypothesis does not stand up to critical scrutiny, and now approach the subject again, hoping that my readers will suspend disbelief and consider the matter with an open mind.

The concept that in Old French ‘verse came first’ applies, of course, both to the history of Arthurian literature and to specific narrative texts. Consequently, Robert's work has been, and is still, on the receiving end of assumptions rather than of analysis. To make any real progress in refining study of Joseph, two situations need initially to be confronted. First, in the early years of Arthurian prose romance, the works which formed the Vulgate Cycle were not direct mises en prose of individual Old French texts (though, of course, they had their sources and inspirations). Second, a shift in perspective is called for, as Robert was not even writing an Arthurian romance. He was telling a story about the Crucifixion, Joseph of Arimathea and the most sacred of holy relics: an eminently suitable subject for treatment within an emerging vernacular prose culture concerned with the appearance of veracity, which, by the end of the twelfth century, included a range of Biblical and ecclesiastical matter.