 The , may have started construction of the walls, replacing an earthen rampart of the late 12th century, and they were completed by William de Valence, 1st Earl of Pembroke after Tenby was sacked in 1260 by Llewelyn ap Gruffydd.Jasper Tudor, Duke of Bedford ordered the walls repaired and improved in 1457.They were raised  in height and widened to allow the garrison to move about freely.