James Stanhope

There was another, toga-like Roman ceremonial garment called the "trabea triumphalis," which, as depicted on diptychs from the 4th through 6th centuries CE, was draped toga-style and worn by Imperial consuls and, in Rome and Constantinople, possibly praetors, when presiding over games in the Roman Circus or Constantinopolitan Hippodrome. The "trabea triumphalis" was heavily embroidered, dyed red or purple, and draped almost exactly like a toga. The 5th-century CE grammarian Servius also describes a "toga trabea" which was dyed red or purple and was worn on various ceremonial occasions. The "trabea triumphalis" might actually have been a more ornamented version of the 5th-century "toga contabulata," since "trabea" in Latin is related to the Latin word "trabs" which means a flat board or beam, and may refer to the flat, board-like draping of the "toga contabulata." At any rate, the "trabea" was worn by Byzantine-Roman emperors from at least the 7th century CE onwards into the Middle Ages, and developed into what in Byzantine Greek was called the "loros" and can be seen on Byzantine-Roman coinage, diptychs, and mosaics from the 7th century CE onwards.

Fifth-century CE decurions probably wore the "toga contabulata" with its characteristic "balteus," which was a stiffly-folded, belt-like drape of the toga which crossed the upper chest and went over the left shoulder. John Lydus (or John of Lydia, Johannes Lydus), a 6th-century CE Byzantine-Roman historian who wrote in Greek at around 550 CE, states that he remembered from witnessing in his childhood town councillors in Asia Minor (now western Turkey) attending meetings "dressed in the toga."

RE: 5th-century CE Roman Togas: In the mosaic from San Vitale shown above (showing Justinian and his courtiers and Archbishop Maximin of Ravenna), Justinian and his courtiers are not wearing togas but the military-style "paludamentum" that was worn by late-Roman Imperial civil servants at public functions. Also, the illustration linked-to by KurtEdwr does not depict a toga but the Greek-style "himation" recommended by St. Tertullian as more appropriate for Christians than the (then) pagan toga. For reliable depictions of 5th-century CE Roman togas, Google images of the Diptych of the Lampadii (c. 425 CE) and also Google images of the consul Areobindus (in Constantinople, later in the 5th century CE). Both items show 5th-century CE Roman aristocrats dressed in the "toga contabulata," a heavily-embroidered toga that was very stiffly folded, like a wide belt, over the chest and left shoulder where this part of the toga was called the "balteus" (Latin for "belt"). After the death of Justinian I in 565 CE, the official use of the Roman-style toga declined along with the use of both Latin nomenclature and even the Latin language in official documents. Imperial officials and Emperors continued to occasionally wear what looks like a vestigial toga, basically a stiff, narrow, gold-embroidered long cloth that was draped like the earlier Roman toga under the right arm, across the chest, and over the left shoulder.