And @eLearningTechie, lest I get too cocky with this "genius" stuff, I got a dose of my own medicine today for another #UCLChemAirPoll class. The HDMI connexion in the remote ICH lecture theatre wouldn't connect. So I did the visualizer/laptop screen trick.
A nice man from AV Svcs turned up after my class. So I turned the projector system back on to show him the problem and the damned problem had gone away. I had been hoist by the old turn-it-off-and-on-again petard. #rookieerror