Deasy, Henry Hugh Peter (1866–1947), soldier, explorer, and pioneer motorist, was born 29 June 1866 in Dublin, second son of Rickard Deasy (qv), privy councillor for Ireland and previously lord justice of appeal, of Carysfort, Blackrock, Co. Dublin, and 27 Merrion Square, Dublin, and his wife Monica, daughter of Hugh O'Connor of Dublin. Educated at schools in Bournemouth and Dublin, he entered the army and was commissioned into the 16th Lancers in November 1888. His regiment was posted to India, and further promotions followed to first lieutenant (January 1890) and captain (February 1894).
He found the routine of regimental life somewhat boring and, noticing that maps of Tibet had large areas marked as ‘unexplored’, determined to travel there. During periods of leave he studied surveying and in June 1896 set out on his first expedition to Tibet and Sinkiang (Xinjiang; Chinese Turkestan). Returning to India in June 1897 he resigned his commission (August 1897), having decided to devote himself to exploring the Tibetan region. He set out on his second expedition in October 1897 and did not return to his base camp at Srinagar in Kashmir till February 1899. During the intervening months he followed a circuitous route through the Ladakh district, the Kwen Lun mountain range, and the Takla Makan desert before visiting the more northerly towns of Yarkand and Kashgar. He also visited the Tangikhol and Khandar mountain ranges and, carrying out trigonometric surveys along his entire route, he negotiated a series of treacherous fords and mountain passes. Enduring extremes of weather, he encountered hostile Chinese officials and local tribesmen who were on some occasions difficult and, on others, downright dangerous. By the time of his return to Srinagar, he had travelled over 5,000 miles (8,000 km).
The information that he had gathered was immediately used by the Survey of India to produce new maps of the region. So detailed were his surveys that his maps remained the most accurate topographical sources of the region well into the 1950s. He had also gathered information on the civil and military administration of Tibet and, echoing the fears of many officials in the government of India, he later wrote: ‘the province is absolutely at the mercy of Russia and will be unfit to offer any resistance when it suits that power to take it’ (Deasy, In Tibet, 354). In 1900 he was awarded the Royal Geographical Society's gold founders' medal for his exploration of Tibet. He later published his account of his travels – In Tibet and Chinese Turkestan: being the record of three years exploration (London, 1901), which described his encounters with local tribes, and was augmented by the photographs of his travelling companion, Arnold Pike.
He was convinced of the potential of the motor car, then still in its infancy, and soon established a reputation as a pioneering motorist. In October 1903 he teamed up with Max Martini to carry out a hair-raising journey along mountain roads in Switzerland. Leaving the Palace Hotel in Caux in a 14 hp Martini car, they motored to the terminus of the mountain-railway line at Rochers de Naye, a climb of 3,200 ft (975 m) during which they sometimes faced gradients of over 1:4. Finishing at a height of 6,640 ft (2,024 m) above sea level, it was a record-breaking drive at the time. Returning to England, Deasy then carried out a non-stop run from London to Glasgow in a Rochet-Schneider car. He later published The problem of road traffic: its solution (1914). He was awarded the British agency for the Martini touring car, but on the outbreak of the first world war he returned to active service, serving as a major on the HQ staff. After the war he went into partnership with J. D. Siddeley, later Lord Kenilworth. Together they developed the Siddeley-Deasy motor car. In later life he retired to his residence at Cnoc na Faire, Carrigahorig, Co. Tipperary, where he died 24 January 1947.
He married (1901) Dolores, youngest daughter of Col. James Francis Hickie of Slevyre, Borrisokane, Co. Tipperary; they had one son and two daughters. Their son, Rickard Deasy (qv), founded the National Farmers' Association.