Bletchley Park, G Block
Block G formed part of the Government Code and Cipher School at Bletchley Park. It was constructed in October 1943. It was home to the ISK and ISOS sections which dealt with the decoding of Enigma and conventional cipher messages from the German secret service. It also housed SIXTA, the Army traffic analysis sections, which dealt with the direction of radio-intercept stations and analysis of the enemy radio traffic. After the departure of the Government Code and Cipher School in 1946 the building was used as a training school for the Post Office and then British Telecom.