On 1 September 1939, two days before Britain declared war on Germany, the station was taken off air with little warning; the government was concerned that the VHF transmissions would act as a beacon to enemy aircraft homing in on London. Also, many of the television service's technical staff and engineers would be needed for the war effort, in particular on the radar programme. The last programme transmitted was a Mickey Mouse cartoon, Mickey's Gala Premier (1933), which was followed by test transmissions; this account refuted the popular memory according to which broadcasting was suspended before the end of the cartoon.

What did the British fear could provide guidance to the German air force?