1. Codex Marcianus attributes the information to the Fifth Book of the Hypotyposeis which was written by Clement of Alexandria
2. Harnack demonstrates that the reference to Britio Edessenorum is only sensible if it was made at the end of the second century CE at the time the king of Edessa "Lucius" Abgar (referenced as "Lucius" in various associated traditions) visited Victor of Rome and a palace devoted to the saints relics at a place called "Britio." The apostles Thaddaeus and Jude are said by the Hypotyposes of Clement to have been buried in Britio Edessenorum. According to Harnack, it is almost certain that the word Britio was misread by some early medieval scribe for an abbreviation of Britannio. Dr. Harnack notices that the see of the bishop of some now unknown city in Arabia, who subscribed the decrees of the Council of Nice, appears in one Syriac list as Britny, which might without difficulty be read as an abbreviation of Britanniae. The tomb of St. Jude in Britio Edessenorum was in the castle—Britium or Birtha—of Edessa, the home of Lucius Abgar IX, and the history of this castle is well known. Hallier says:— In the south-west, on the spur of the mountains of Edessa, stood the citadel, containing the winter palace of King Abgar IX, which is reached by the high-road known as Beth Sahriyé. (Arnold Harris Mathew, The English Historical Review XII. No. LXXXVIII, 3 - 4 In the ninth-century Chronicle of Edessa it is stated that ‘in the year 205 Abgar built the Birtha (palace) in his town.’ St. Jude’s tomb has been pointed out in the city of Edessa certainly from the third* century, and the Birtha , or castle , of Edessa is the Britium Edessenorum where Lucius Abgar resided. (Arnold Harris Mathew, The English Historical Review XII. No. LXXXVIII, 1907, 769 - 770)
As such, not only is Clement of Alexandria the likely "Clement" of the tradition, the tradition is best understood as having encapsulated a list of places saints died at the end of the second century, the time Clement is known to have been active.
