The mountains were the great love of Una Cameron's life. She was fascinated by them since her childhood, during her "enforced" stay in Switzerland. Her summer holidays in the Alps gave her the joy of her first climbing excursions.
Her passion for the mountains also influenced her friendships. In Rome she met Hazel Jackson, an American sculptress who shared her interest for mountain climbing. They both took part in climbs organised by the local branch of the Club Alpino Italiano and made important climbs in the Apennines and in the Dolomites. In 1929, Miss Cameron was accepted as a member of the Ladies Alpine Club in London.
Her meeting with the guides of Courmayeur around 1930 marked a turn in her mountaineering experience. Édouard Bareux and Élisée Croux enabled her to discover the excitement of the mountains. Their relationship was made of mutual respect and friendship, but they also had a special way of teaming up, a result of the long moments they spent together.
Miss Cameron longed to meet the challenge of climbing the giant peaks of the Alps. The idea of a triple ascent of the Mont Blanc by the Sentinella Rossa (the Red Sentry way), the Via Major (Major way) and the Via della Pera (way of the Pear) was suggested to her during a conference held at the Ladies Alpine Club in London in 1932, by her fellow countryman Graham Brown, who had made the first two ascents in 1927 and 1928 together with F.S. Smythe. Miss Cameron was fascinated by this project and she began her own attempts to climb the "Roof of Europe". In 1935, she succeeded first of all in crossing the Peuterey Ridge, accompanied by her friend Dora de Beer, the guides Élisée Croux, Édouard Bareux and Mario Rey, and the porter Mario Cosson.
Three days later, she took the first of the three routes explored by Graham Brown, the Sentinella Rossa. She took the second route, the Via Major, in 1938 but was never to attempt the third route, the Via della Poire.
During these same years, Miss Cameron and her inseparable guides undertook numerous expeditions outside Europe. In 1932, in the Caucasus, despite a thousand problems and adverse weather conditions, she succeeded in climbing 7 peaks in the only 6 days of good weather. In 1935, she was in Canada to follow a mountain ski route in the Rocky Mountains. But her most outstanding achievements were to take place in Africa, in1938. She was the first woman to climb Mount Kenya (5 200m), to reach the summit of Mount Kilimanjaro and to attempt to climb the Ruwenzori, the "King of Mists".
The outbreak of the Second World War prevented her from carrying out her projects for new expeditions, including a journey to Patagonia (Argentina).
After the war, she got in touch with her Courmayeur guides, hoping to complete her project of the triple climb, but by now, the days of her mountain exploits were over and she could enjoy the mountains only from below. Even after her she eventually returned to Britain, she kept a deep affection for this country and its people.