Key PointsAn extended edition of the 1999 best sellerVery well illustrated with many previously unpublished pictures Description Following the First World War, anxiety was building following the graphic demonstrations of air power during the conflict. London and other major cities had been bombed by the Zeppelins and, later, the Gothas, causing some 5,000 casualties, 1500 of which were fatal. Air defence therefore moved up the agenda and the detection of incoming aircraft became a priority. With RADAR not even the germ of an idea until 1935, acoustics offered the only practical solution. Based on the successful acoustic gun ranging on the Western Front, key members of that research team now focused on the detection of aircraft. With present day interest growing in the history of acoustics with, for instance, the rediscovery of the early sound mirrors at Fan Bay, near Dover, together with the tangible relics of the sound mirrors which still exist, Echoes from the Sky is set to resume its place as a best seller.