BBC interview about the sound mirror in Redcar: “In 1916 it was sitting in open farm land. Since then a modern housing estate has grown up around it. The concrete structure has not always been treated well. When it stopped being used to detect German raids a farmer used it as a spot to store manure. There have been problems with bike enthusiasts using it as a ramp to practice their stunts.” Release date: 22 January 2014.