P survives in a single medieval manuscript:
Aberystwyth, National Library of Wales, MS. Peniarth 20, written c.1330, probably at the Cistercian abbey of Valle Crucis (Llanegwestl).
Gutun Owain was closely associated with the Cistercian abbey of Valle Crucis where he was the principal scribe of the S text of Brenhinoedd y Saeson preserved in Llfyr Du Basing, 'The Black Book of Basingwerk', and where he may have been responsible for the continuation of that chronicle from 1333 to its end in 1461 (Dumville 2005).