Recent (Spring 2012) extensive burning of gorse on the southern slopes of Mulfra Hill has revealed a probable prehistoric field system. A fallen standing stone was recorded on the slopes by William Copeland Borlase in 1872 and mentioned in Vivian Russell's 1971 West Penwith Survey.
I didn't know about the stone on our recent visit, so didn't look for it. It is mentioned in issue 78 of the excellent Meyn Mamvro magazine (which is when I realised what I'd missed).