During the Second World War, the British Government established the Special Operations Executive (SOE) for the purpose of coordinating ‘all action, by way of subversion and sabotage, against the enemy overseas’. Although the overseas operations of this branch of the British Secret Services are relatively well known, no previous study has assessed the organisation’s UK based infrastructure. This thesis represents the first time the entire UK property portfolio of a clandestine government agency has been assessed. By addressing this gap in our knowledge, this thesis has increased the number of identified properties operated by SOE by 30%. This was achieved by undertaking a desk based assessment which combined pre-existing historical and archaeological methodologies. At the start of the Second World War, there were few existing facilities established within the UK to support clandestine operations. As the conflict progressed, in parallel to learning the operational procedures of their trade, SOE also had to rapidly expand their support infrastructure. The organisation could only effectively function by establishing facilities dedicated to training, research and development, supply, transportation, communication and command and control. These facilities, when required, combined reflectivity and innovation. It was, however, SOE’s preference to utilise pre-existing structures, where feasible, instead of erecting new buildings. Those facilities which were constructed were generally unique to the organisation. By assessing SOE’s UK property portfolio, this thesis goes some way to countering the often held notion that the organisation was ‘amateurish’.