OS 1st edition mapping shows a small rectangular building, measuring 9m x 4m, abutting to the fence. Associated with Fort Belan (see NPRN 26459). Modern aerial photography shows that the building has been replaced with hard standing for a caravan.

Sources include:
NAW aerial photography 2006-9
OS 1st edition 25in mapping

Maritime Officer, RCAHMW, July 2013