The information board near the car park states that the wall is not prehistoric.
I think it said it was mediaeval but I can’t be sure.
I tried to write the information down but it was raining so my paper got wet and I couldn’t write on it!
The walls in question are easy enough to spot around the stones – in fact you need to climb over one section to get closer to some of the rocks.
A Tor Enclosure to be exact. Mentioned by Craig Weatherhill, in "Cornovia: Ancient Sites of Cornwall & Scilly" (Cornwall Books - 1985, revised 1997 & 2000) - "On the slopes of Helman Tor are the remains of a field system including at least one round house. The summit of the hill is enclosed by the battered remnants of an earth and stone wall linking the natural outcrops of rock. This enclosure is long and thin, measuring 170m from north to south, by 60m. It is similar in size and construction to the Neolithic village enclosure on Carn Brea. The site has been dated to the 4th millennium BC."