Crows, or, more specifically, cormorants, have come to my attention. It started with Toldhu, translated as 'black hollow', or Mullion Island, where cormorants are annually ringed. I wondered if the nearby Loe, a freshwater inland lake, separated by Loe Bar from the sea, was a cormorant fish-pond as it were.
Looking at Google Earth, Mullion Island is just offshore from Mullion Cove on the Lizard Peninsula, and on the Michael-Apollo Line or whatever it's called.

There is a clear view across Mount's Bay to St Michael's Mount. So tracking this putative line, it crosses the peninsula north-east to south-west, ending up at Church Cove where nowadays there is a lifeboat station (not an uncommon association I have found).
The route goes across Predannack Airfield, built in 1941, which suggests the terrain was relatively flat, and then, unexpectedly, past Mount Hermon. There are two St Rumon, also spelt Ruan, churches, now disused, one on the north side of Mount Hermon and the other to the south-west. Both have springs or wells attached. 'Nothing is known' about this St Rumon whose name sounds like a transliteration of Hermon.