A deep-seated landslide with base failure occurred on the 80m high slope of an open-pit clay mine used for cement production. The scarp of the landslide lay close to the ruins of a prehistoric settlement with important archaeological findings. The need to protect the archaeological site from possible retroggression of the landslide called for the design of serious stabilisation measures. On the other hand, in order for the operation of the mine to remain economically viable, these measures were limited to excavations for scarp unloading and drainage of surface water. The paper presents the characteristics of the landslide mechanism and the measures designed to stabilise the landslide.