Last Sunday I was on a warm up route at the LHS of Bram crag quarry with a mate. He'd just led the route (combination of Bolt from the blue and Looper) We pulled the ropes and I led it....just before the last clip on the upper section of Looper, a lump of rock about the size of a large frying pan and 4" thick dropped from a series of underlings above me and twatted me on the leg. Fortunately it had only dropped a metre before it hit me (bruised leg and fortunately I managed to cling on) and just missed my mate below. Had I been 5m lower it probably would have taken me out serious fashion. I had not touched the piece of rock, it just decided to drop off when I was near it. My mate doesn't think he used when he was clipping the bol on his ascent. We are both older experienced climbers in the age range 57-60, capable of 7a onsite sport climbing and currently E2/3 trad (though both have led up to E4/5 when we were younger) We were both aware of loose rock at the quarry. At least one of us wont be going back there to climb again.