A major development or reconstruction phase took place in the 1230s, possibly completed by one of the de Morville daughters as the male line had died out. Pont states that Dorethea de Morville, daughter of Richard de Morville and wife of Philip de Horssey, 'accomplished' the fabric of the monastery. De Morvilles mound at Dreghorn was supposed to have commemorated a daughter of the family, drowned at the Holm ford; any possible link to the abbey is unrecorded. The two towers and the west transept seem to have been added on in the 1250s.