The Hon. Desmond Guinness is the second son of Bryan Guinness, 2nd Baron Moyne and his first wife Diana Mitford (later Lady Mosley). He was educated at Eton, Gordonstoun and Oxford University. He became a writer on Georgian art and architecture and a conservationist.
In 1958, he and his first wife, Mariga (the former Princess Henriette Marie-Gabrielle von Urach), founded the Irish Georgian Society to help to preserve Irish architecture. The couple bought and started to preserve historic Castletown House, in County Kildare, said to be the finest Palladian house in Ireland. He also bought Leixlip Castle, County Kildare, where he continues to live with his second wife, Penelope Cuthbertson. Guinness also has been a trustee of the Iveagh Trust and the Kildare Street & University Club. He's the grandfather of fashion model Jasmine Guinness.