Extreme sports special: 'I get the urge to jump when I'm standing on the edge'

From avoiding lava bombs while volcano boarding, to slacklining over a 300ft gorge. What makes some people risk their life for their sport?

Any snowboarder visiting the island of Tanna in the South Pacific, as I did in 1995, would have had the same thought when they set eyes on its volcano. Mount Yasur has a near-vertical, 1,000ft pumice slope on its north side, and I looked at its treeless, virgin face and said to myself, "I've got to go down that."