Going well over the first half, including in the rocky areas. Then concentration fell away as I got tired. Several controls of just running into the circle and hoping I'd spot it in among the rocks - not the way to do things.
The error at 11 was not really my fault. The control description was southern end of rocky ground, and indeed that's where the control was hung. But the mapped rocky ground stopped about 50-75 metres north of the visible rocky ground, so I lost time on that.
And so I was heading off to number 12 from a point 50-75 metres south of where I thought I was, explaining why I couldn't understand the rock features I was seeing - leading to another mistake.