The Sentinel is a massive quartzite standing stone, the first ancient monument we met as we walked up Mynydd Llangyndeyrn, which translates from the Welsh as the Mountain of the Church of Saint Cyndeyrn. The stone was flat on the ground until 1976, when its socket was found and it was re-erected. Nobody is sure what the stone signifies although it may have been a way-marker and some think there may have been another opposite, forming a portal to the Bronze Age landscape of the Mynydd. As I circled the stone, looking for the right angle to draw it, I noticed the coastline in the distance. I was on the mountain with archaeologist Dewi Bowen and film maker Melvyn Williams and Dewi told me that the coastline was North Devon, around the Bideford area. Coincidentally I had some Bideford Black in my bag and so decided to use it to draw with. It’s a strange oily black pigment, a bit like coal, that used to be mined commercially in Bideford until the late 1960s. Local artists still dig it out and use it and I was lucky enough to be sent some back last year. It’s very possible that Bideford Black might have been traded and used many thousands of years ago.