An automatic volcanic ash detection system has been developed by the Met Office for use by the London VAAC. It searches infrared images from Meteosat for clouds that are near to a volcano and have a shape that might be expected for volcanic ash given the local wind and temperature conditions. With system parameters set to detect 7 test eruptions, the system has detected an eruption of Etna but missed an eruption of Montserrat. The false alarm rate is currently too high for the system to be of operational use. However if the expected cloud shapes can be better defined, and consideration is given to the temporal and spectral characteristics of volcanic ash, then it may be possible to reduce the false alarm rate to a more acceptable level.