In 1939, the total audience for the BBC's programmes had grown to an estimated audience of 100,000 viewers, watching on 20,000 television sets. However, BBC television broadcasting ceased on 1 September 1939 in anticipation of World War II. The station remained off-air for the duration of the conflict. The British Government were afraid that the VHF transmission signals would act as a guiding beacon for German bombers targeting central London, and the technicians and engineers of the service would in any case be needed for war efforts such as the radar programme.