Had to look that one up!
Lichens, yes excellent indicators of air quality. I would say that when I purchased my present house on the edge of Northampton it already had thick lichens on the roof and it was only 6 years old at the time. The environment down in Cornwall is most likely cleaner, so I am not surprised by the growth on the stones. The summit area itself is damp in places with sphagnum moss established - another indicator. Anyway, it matters not when the landscaping was carried out, only whether or not it is likely to be added to and having been on rhe summit I am happy to say that my initial concerns over that possibility have been allayed.
73, Gerald G4OIG
I would just like to remind everyone that if you would still like to activate Hensbarrow Beacon G/DC-004, you only have until the 31st August to do so, after then this summit will no longer be valid for SOTA. However from the 1st September Hensbarrow Downs G/DC-008 will become a valid SOTA summit.
G - Association Manager