The proposition that Diego de San Pedro was a Jew has by now more or less established itself in the literature. Menendez y Pelayo was the first to notice the anecdotes in Luis Zapata's Miscelanea which insinuate that “el que trobo la pasion” was not a cristiano viejo; and Menendez y Pelayo is almost certainly right in assuming that Diego de San Pedro is intended: “entre las pasiones trovadas ninguna fue tan popular como la de Diego de San Pedro”. But these anecdotes are not, of course, proof positive of the proposition. The concrete documentary evidence for it was supplied by Emilio Cotarelo y Mori in 1927.