Gawaine Leslie Rowan-Hamilton was born on 2 April 1923. He was the son of Brigadier Gawain Basil Rowan-Hamilton and Phyllis Frances Blackburn. He married Mary Bridget Blakiston-Houston, daughter of Lt.-Col. John Matthew Blakiston-Houston and Lettice Arden Stobart, on 4 September 1956. He died on 6 February 2014 at age 90.

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He was also known as Gavin. He was educated at Wellington College, Wellington, Berkshire, England. He was educated at Corpus Christi College, Cambridge University, Cambridge, Cambridgeshire, England. He fought in the Second World War in 1942, where he became a POW. He gained the rank of Captain in the The Black Watch. He was with the Foreign Service in Far East between 1949 and 1953. He was a land agent. He was appointed Fellow, Royal Institution of Chartered Surveyors (F.R.I.C.S.) in 1970. He lived in 1976 at Stenton House, Stenton, Dunbar, East Lothian, Scotland.