In reply to Stanners: We did it a week ago, intending to do it with head torches but I was in charge of packing them so obviously they were forgotten! At one particularly dark point on pitch two I thought one might have been useful for the leader, and was regretting not packing it, but really it's more exciting and interesting without a light.
I later found that I had actually packed the headtorch, but forgotten where I put it...