however, modern scholarship has established that all surviving welsh variants are derivative of geoffrey rather than the other way around. roberts has shown the "brut tysilio" to be "an amalgam of versions", the earlier part deriving from peniarth 44, and the later part abridged from cotton cleopatra. it survives in manuscripts dating from , and roberts argues that a "textual study of the version […] shows that this is a late compilation, not different in essentials from other chronicles which were being composed in the fifteenth century".