Gary is known as one of the great leaders in the mountaineering world (per EverestNews.com)
He has led many expeditions, often with his late wife Ginette Harrison, including to the summit of K2, Kanchenjunga (three times), Shishapangma, Makalu, Dhaulagiri and Lhotse. All of these expeditions, with the exception of Everest, were achieved without the use of High Altitude Porters or supplementary oxygen.
Gary has summitted Everest, Cho Oyu, Ama Dablam, Kilimanjaro via the Heim glacier, Mt Logan (third unsupported alpine style traverse of East Ridge) among many others. He has led treks throughout the Himalayas and Karakoram including Lunana Snowman, Manaslu Circuit, Dhaulagiri Circuit and Snow Lake with Hispar La.