(Very) slack lining

We were orienteering on Holme Fell today. It has old slate mines, which include a rather fine hole about 30 - 40 metres deep, across which this guy was attempting to slack line. He wasn't very good, but he tried hard. The blip is a sequence of balance and optimism, unsteadiness, a fine dive and finally, resignation. I couldn't do it but it looks good fun.