Dennis was born in 1922 in Belfast of a linen producing family. He was educated at Sedburgh School in England, and started work at Harland and Wolff shipyard in Belfast. In WW2 he was trained as a pilot in Canada on Tiger Moths, moving on to the Halifax and Lancaster in Bomber Command, and becoming a member of Pathfinder Force. Post war he flew Lancastrians and Tudors in Don Bennett's British South American Airways (BSAA) and on the Berlin airlift. A keen sailor he participated in the 1948 Olympic Games in the Dragon class and was made a life member of the Royal North Ireland Yacht Club. He flew on African and East Asian routes in Argonauts, DC-7s, and 707s and was a licensed celestial navigator. He married Joy Elliott, a former BSAA stewardess and they had 2 children. Dennis came to Australia in 1966 to fly business jets, but became an instructor for Qantas on 707 and 747 simulators. He retired in 1982, moving to the Sunshine Coast and was a member of PFFA and QAM. Notably, he was able to arrange acquisition and transport of aircraft components from the UK to Brisbane. Following the death of his wife, he moved to the Coffs Harbour area to be with family, and passed away in December 2004 after a series of strokes.