The climb that the accident happened at was at Hedbury Quarry, an area we had climbed in before along with several other local spots. Skill level, 1 begineer but has joined the local Wessex climbing group and participated in local courses. 1 intermideate and 1 experienced (10 years of sport climbing experience). Objective, the two more experienced climbers were planning to set up a top rope. Route, dry time climb. Hazard Evaluation, we looked at the route from top to bottom to plan the climb, asses bolts and hardware at the top. We did notice some water seepage on the higher outer right edge of the route - but it was not located near the rock which fell. The rock was not noted as looking precarious or loose. Passer by had commented that he had just done the route and discussed how he had completed it. We pre clipped first quick draw. Checked knots and harness and gear. Weather, sunny and dry. Incident, shortly after the lead climber had clipped in the second bolt , weight was split evenly between four secure points (left hand placed in rock in question) as the climber transferred weight onto left side to reposition his right hand, a large rock (3ft x 1ft x 1ft) broke free of the main face. Knocking out the climbers left foot causing the climber to rotate and fall. The fall was arrested by the belayer before the climber hit the ground. The climber only sustained minor Injuries. The rock had continued to fall for two metres before striking the belayer on the left shoulder. The extent of the damage was not clear at the time however a passer by saw the incident and immediately went to call emergency services for help. Two doctors and a paramedic from Southampton climbing club had come over to help and did an initial assessment of the belayers condition and put the left arm in a sling. No broken skin or visibly broken bones but clear that some damage had been done and upon consultation with the doctors it was decided to move away from the rock fall area. Once up and as the casualty could walk it was decided to continue to the top of the quarry to ease access for emergency services. Once at the top we were met by HM coastguard volunteers and ambulance crews. Helicopters (air ambulance and coast guard) had arrived but were called off before landing. Casualty was then transferred to poole hospital. The belayer had sustained AC joint dislocation, a transverse process fracture (C7, T1 - T4) and minimal pneumothorax.