I was running a group abseil session for a charity group. The participants were abseiling down an overhanging wall, and I was placed at the top of the wall to supervise and belay them. I'd make sure they set up their abseil device correctly, and belay them using an Italian hitch as a safety back up. Halfway through the session, there was an altercation between some of the group members, which the other instructor was struggling to deal with. I unclipped from my personal safety lanyard and went down to assist. The situation got pretty stressful and the decision was made to abandon the session and return to base. Two of the participants, whose behaviour had been exemplary, pleaded with me to allow them to have their turn, and thinking they'd been hard done by, I agreed to quickly belay them on their abseil. As the first one descended, I leaned out, holding onto the belay rope to check they had reached the floor. It was at this point I realised that I had not re-attached myself to my personal safety lanyard, and was only kept in place because I had a firm hold of the belay rope which ran into an Italian hitch behind me.