Johannes Alanus was an English cleric who was a favorite of King Edward III. Alanus (also known as "John Aleyn") made the rounds of the monasteries in Kent collecting taxes in the years following the Black Death. In 1362 he was awarded one of the 26 canonries in St. George's Chapel in Windsor and was named a chaplain in the Chapel Royal. Alanus served in these capacities until his death in 1373, willing a manuscript of his musical works to St. George's. It is not known to presently exist. Alanus is in three manuscripts accorded the authorship of an extraordinary and complex motet, Sub Arturo plebs vallata/Fons citharizancium/In omnem terram exivit. It appears in the Codex Chantilly, the so-called "Yoxford" manuscript, and the tenor alone is shown as an example in a treatise found in the mid-fifteenth century Italian source known as "Q 15" in Bologna. Alanus is also credited with two German Lieder, a virelai (also in the Reina Codex), and an un-texted fragment in the lost Strasbourg manuscript that was copied by Charles Coussemaker (Strasbourg: Bibliothèque Municipale 222 C. 22). This last-named source is notoriously unreliable in terms of attributions to composers. But it is the motet Sub Arturo plebs that provides the greatest challenge. It was written for a festive occasion and the text mentions the names of some 14 musicians, including Alanus (or "Aleyn") himself. Over the years various scholars have advanced the foundation of the Order of the Garter in 1349 or the ceremony celebrating the victory of Potiers (April 23, 1358) as possible events for which Alanus' motet was written. But a detailed examination of the musicians named shows that it could not have been composed before 1370. In stylistic terms, the motet is of a kind more germane to the early fifteenth century than to the 1370s; were it written later than 1373, then Johannes Alanus the cleric is not the same person as Johannes Alanus the composer. Most English musicologists are more comfortable with accepting the latter scenario than to change their whole notion about the development of musical style in the mid-fourteenth century. It remains a mystery. Two additional works ascribed to "Aleyn" in the Old Hall Manuscript and a third so-designated in Strasbourg were also once considered the work of Alanus, but are now thought to belong to a later composer of that name.