Chessell has been climbing since 1988, guiding since 1994, and has climbed and guided on all seven continents. He started out on the crags and in the gorges of National Parks of Australia, then moved on to larger mountains around the world. He is one of few Australian mountaineers to have climbed and guided Mount Everest and the first South Australian to summit. He has summited Mt Everest three times, in 2001, 2007 and 2010. His ascent in 2010 was from sea level, riding 1600km from the ocean in India.