The following pictures were taken in 1977 by station personnel. It looks like the survey was done in slightly inclement conditions, not unknown on Unst. (Left click on pictures to enlarge).
These pictures, together with other supporting material, were sent to higher authority to back the bid for reconstruction. I should imagine the case went onto HQ 11 GP, then to HQ STC, then to MOD and then back along the route in reverse. Authority was eventually given and rebuilding went ahead at the end of the top site reconstruction phase. The work was carried by the Shetland Islands Council – the only organisation in the Islands capable of undertaking such a job at the time – and was funded by MOD with taxpayers’ money. I’m fairly sure it wasn’t covered by the NATO infrastructure funding.