This last segment of a three-part study describes the Carolingian technique of wall painting, the plaster medium, the sketches, pigments and glazes used. The Romanesque paintings are also examined. The condition of the murals is described, and the deterioration attributed to 1) integral weaknesses in the painting technique; 2) unintentional damage caused by well-meant renovation work which in fact accelerated the damaging effects of weathering. The measures taken since 1965 are listed. Other measures are under consideration prior to a new restoration project due to start in 1989.