Some of the routes at Gold Diggings Quarry require a scramble/traverse around the edge of the lake to access the base of the climb. As I wanted to top rope the route I built a anchor using a semi static rope using a large rock and a stake approximately 4m & 7m meters back respectively. The strong point of the anchor was approximately a meter from the edge. My belayer then tied in and connected to the anchor using a clove hitch and sat on the edge. I then abseiled to the bottom, my belayer sat at the top and belayed from the hip using a GriGri. Nearing the end of the route I made a big move and fell off, as the belayer took my weight they were pulled from the ledge and left suspended. Unable to self rescue I was lowered to a ledge and traversed to safety. I then walked around and pulled my belayer up to safety. The edge of the rock was fairly sharp, after the fall the single strand which the belayer anchored with was running over the edge and supporting both of us. The rope looked ok but had a soft spot which I have cut out. The belayer had a minor injury to the finger and a sore shoulder. A lucky outcome!