Swiss mountaineer Ueli Steck was training for a new record in April 2017: Climbing Mount Everest, descending via the South Col and re-ascending the Lhotse...all without supplemental oxygen. (SRF/swissinfo.ch)
Ueli Steck has made a name for himself by winning several speed climbing records on the Eiger North Face over the last few years.
In 2013 Steck made the first solo ascent of Annapurna in the Himalaya, winning the most prestigious climbing award, the Piolet d'Or, for the second time.
A year earlier he was involved in a highly publicised fight that broke out between his team and a group of Sherpas on the west face of Mount Everest.