Streather was originally commissioned into the Indian Army where he saw service towards the end of the Second World War. He transferred to the Gloucestershire Regiment in 1947 and was immediately awarded his "war rank" of Lieutenant. He promoted to Captain in 1953 and to Lieutenant Colonel in 1967.
As a captain posted to the Chitral region of Pakistan, Streather was the official government representative in a Norwegian expedition that made the first ascent in 1951 of Tirich Mir (7,710 m), the highest mountain of the Hindu Kush. He was initially appointed transport officer, but became a member of the successful summiting team On his return to Britain he was invited to join the Alpine Club (he later became its president), and was selected for trials for the 1953 British Mount Everest expedition. He was rejected for the latter because of a lack of technical experience, but nearly at the same time was invited to join the 1953 American Karakoram Expedition, which attempted a far more technical route up K2, the second highest mountain in the world. Though again originally in charge of logistics, he climbed as high as anyone else and was involved in the dramatic events at 7,800 m. In 1955, Streather participated in the first ascent of Kangchenjunga, the third highest mountain in the world. With Norman Hardie, he reached the summit the day after the first summit party of Joe Brown and George Band. In 1957 he survived an epic near-ascent of Haramosh (7,397 m). In 1959 he led a successful expedition that included an ascent of on Malubiting Southeast (6,970). In 1976 Streather led the Joint British Army, Royal Nepalese Army Everest expedition, which successfully put two British Army climbers on the summit: Bronco Lane and Brummie Stokes.
In 1965 he was he was appointed a Member of the Order of the British Empire in the New Year"s Honours and in 1976 he was made an Officer of the Order of the British Empire. He was initially appointed transport officer, but became a member of the successful summiting team
