The South African, who grew up in the apartheid era, tackled the world's highest mountain in 1998 as part of the "Everest North Ridge" expedition.
He did not make it to the top but took many positives from the experience, which he describes as a "spectacular failure".
It prompted him to face other adventures in his life and he now works for the New Zealand Volunteer Service Abroad programme.
Johnston hopes to motivate and inspire people and spoke to athletes and other officials at VASANOC.
