29Horn, Walter, Jenny White Marshall, and Grellan D. Rourke. The Forgotten Hermitage of Skellig Michael. Berkeley:  University of California Press,  1990. 71-2.
The explorers initially did their exploration on their own time, using mountaineering equipment and calling in helicopters when necessary.
It was the workers from Ordnance Survey who first noted possible structures on the South Peak in 184 (pp. 15-16).