Gary Hemming is a trained climber in Yosemite Valley. He moved to France in the early sixties and took university courses in Grenoble, while climbing with John Harlin. Gary Hemming had a son with Claude Guerre-Genton in 1963. He participated in the opening of committed climbing routes in the Mont-Blanc massif, among others with John Harlin, Tom Frost, Stuart Fulton and Royal Robbins.