Shapley Tor Inscribed Initials

Acknowledgement: Martin Philpott kindly supplied the NGR and following information: “I’ve visited Shapley Tor again and come across two sets of initials carved into the face of one outcrop, I’ve included the NGR. One set is easy to recognise JC but the other set which is on the same front is not so easy to read.

Does anyone know what these initials denote, or to whom?