I was seconding a route and realised around 20 feet off the ground that my right leg was not in my harness leg loop. The rest of my harness was on correctly. I was able to get my leg in the loop without too much trouble as it had a buckle I could unclip whilst staying safely in the rest of my harness. My climbing partner had checked me at the bottom before we set off.
8 of us were in the group at Chairladder for some relatively simple multi-pitch trad climbing. Some had climbed there before, others had not. All party members were experienced climbers to varying degrees. The weather was excellent, clear, little or no wind, sea state calm. We all abseiled in next to Terriers Tooth. Party  of 2 were climbing Terriers Tooth, party  of 3 were on Diocese (I was leading this route), party  of 2 climbers were on Flannel Avenue. A single climber was taking pictures from the base and was autonomous. At the time of the incident: Party 1 leader was on the mid-height belay, bringing up second. Party 2 leader was at the 2nd belay (having run pitches 1 & 2 together to belay at the same spot as Flannel Avenue), bringing up both seconds. Semi-hanging belay to maintain view of both seconds under the roof. Party 3 leader was on the top crack of the top pitch of Diocese running 2nd of Flannel Avenue with top of diocese 3. Second was on belay near to party 2 leader. Incident: At approx 12:00 Party 2 leader witnessed the end of a fall that leader of party 3 had taken from the top pitch of Diocese. The leader was now inverted in a star position and had sustained an obvious head injury which was bleeding. The leader was unresponsive, but moving in what looked like a daze. The party 3 belayer had held the fall, but had not witnessed it, being slightly higher and to the left of party 2 leader (who was on the arete in a semi-hangin belay). The casualty remained unresponsive for approx 1 min. until they did respond in a vague manner and then did re-right themselves after a further 30-60 seconds. Communication with the casualty was good thereafter. Whilst a response was being sought, leader party 2 communicated with party 1 (Terriers Tooth) and told them of the incident, asked them to make their way to the top of the crag asap and prepare for evacuation. Single photographer made their own way to the top via abseil rope. Party 2's seconds then arrived at the belay. Second 1 attempted to contact emergency services, but signal was weak. Second 2 arrived at belay shortly afterwards. A swift battle plan was put in place: Second 2 would lead through, check the casualty over, make safe and proceed to top of crag to bring others up so as to hoist casualty asap. Second 1 now did contact emergency services through text service. Second 2 proceeded to reach casualty, check and make safe before leading on to the top of the 3rd pitch. Party leader 2 now followed, checking casualty again, talking to them before proceeding to top of 3rd pitch. By now, party 1 was at top of pitch 3 waiting for action. At that point in time 2 other climbers were noticed walking down to the abseil point and were asked to assist - which they did without question (many thanks for your help and input Martin and Jamie). Party leader 2 sort of took the lead role, in terms of shouting out and rationalising options/alternative suggestions from all party members. The decision was made to 'man-handle' haul the casualty to the top of the crag. With 7 people now at the top of pitch 3 (not entirely safe ground, but managable with plenty of belay points) there was plenty of strength available to do this. Party 2 second 2 who had led up to the casualty stayed at the edge to act as persistant belayer and 'banksman' for communication between haulers and casualty. Party 2 second 1 was belayed up to be with casualty by party second 2. Continuous input from all sides was rationalised to add a main belay to the haul rope and back up with an auto-block. Others made safe to flakes etc. A rope was lowered to the casualty and on the instructions of the banksman/belayer the rest of us hauled the casualty to the top. There were a few stops, but this only took perhaps 2 minutes. Casualty was now at the top of pitch 3 and was still needing to get to completely safe ground. At this point it became apparent that they had also injured both ankles and were having trouble walking. They were assisted around boulders and obstacles to safe ground by group members leapfrogging around them protecting the way and assisting with removing weight from ankles until a fully safe position was arrived at. This was right next to the coastal lookout station and this was open so the casualty was removed to there to be made comfortable. Remaining persons were belayed to the top of the crag and all were at top within one hour of incident. Further conversation with emergency services to confirm ambulance. Member of party 1 was dispatched to meet with the ambulance and guide them to the site. Ambulance arrived at 13:15 - examined casualty as not in immediate danger, but took to hospital for complete check up. The ambulance having left, the rest of us called it a day @14.00. The casualty was cleared later that evening and was back with us.