These two have been commandeered as gateposts and probably have always been just that, but there’s always the possibility that there was once more to it....
Carn Ffoi is a great spot to visit if you are in the Carn Ingli area, and has a high concentration of Psilocybin in the autumn. Perhaps ‘They Were On Hard Drugs’?
Perhaps not just humans… I know that moose in Scandinavia love Fly Agaric, and have mused that perhaps other animals, eg the sheep you think are pretty dim, standing in roads etc might in fact be off their heads on the October bounty