The manuscript Lewis E 22 at the Free Library of Philadelphia has an uncommonly complete provenance. Written in the late twelfth century at Santa María de Benevívere in the Tierra de Campos of Palencia, Spain, an ex libris inscription on the last lines of the final folio records its origin, with an enigmatic addition by a later hand with the name “Didacus.” Following the exclaustration of Benevívere in the nineteenth century, the manuscript passed through a series of collections in England and Canada before it arrived in the United States with John Frederick Lewis, including those of William Braggeand George Dunn. Furnishing new evidence for its provenance and contextualizing its creation at Benevívere, this paper offers a new interpretation of the Didacus inscription as a memorial to the monastery’s founder, Diego Martínez de Villamayor (d. 5 November 1176).