Isabella, until he was executed in 1330 by Edward III. Cefnllys was forfeited by the Mortimers as punishment but returned to the family the following year. Repairs of the castle and its hall were carried out from 1356 to 1357, and at the outbreak of the Welsh uprising led by Owain Glyndŵr in 1400, Cefnllys was in temporary royal custody. Records show that it was defended by a well-provisioned force of 12 spearmen and 30 archersa detailed register of supplies sent to the castle in 1403 survives. This may have been insufficient, as a 1405 grant to Richard Grey described the lordship as "burned and wasted by the Welsh rebels", though it is unclear whether the castle itself was sacked or if the destruction was limited to its hinterland. The castle survived into the 15th century in a reparable state, but its upkeep was increasingly neglected as advances in warfare and shifting social patterns undermined its importance. The death of Edmund Mortimer, 5th Earl of March, of plague in 1425 marked the end of the Mortimer male line and the castle was inherited by Edmund's nephew Richard, Duke of York, who paid for repair work and appointed officials from a new class of Welsh office-holders to manage his distant estate. Throughout the Marches, minor Welsh nobles were rising to positions of local power, and they preferred the comfort of oak courts to draughty stone castles: in the view of historian Richard Suggett, change was "expressed architecturally by the decay of the masonry castles... and by the building of new timber halls at or near the castle sites by the Welshmen of influence within a lordship". The pre-eminent mid-15th century travelling poet Lewys Glyn Cothi composed four poems regarding Cefnllys, including one which describes such a hall on Castle Bank. The poems, which survive in a manuscript from 1468 (although they probably date from 1432 to 1459), praise the Welshman Ieuan ap Phylip, who was constable of Cefnllys Castle and receiver of the lordship of Maelienydd. Ieuan had a two-storey hall built to exhibit his status and entertain guests, and, uniquely, Lewys' poetry records the name of the master carpenter as Rhosier ab Owain. The accession of Richard's son and heir, Edward, to the English throne in 1461 caused Cefnllys to become crown property. It was included in a grant of predominantly ruined castles to Prince Arthur by Henry VII in