Bury, Lady Mairi (Elizabeth) (1921–2009), gardener and philatelist, was born 25 March 1921 at Mount Stewart, Co. Down, youngest of four daughters and one son of Charles Stewart Henry Vane-Tempest Stewart (qv), 7th marquess of Londonderry, and his wife Edith Helen Vane-Tempest Stewart (qv). She was registered at birth as Mary, but from her youth used the form 'Mairi'. She was much younger than her four siblings, and her eldest sister married the year before she was born. Her second eldest sister, Lady Margaret Vane-Tempest Stewart (d. 1966), was an enthusiastic aviator and a war correspondent, apparently the first woman reporter to cross the Rhine with the Allied troops in 1945. Lady Mairi was privately educated, and much of her childhood was spent in the magnificent surroundings of Mount Stewart. From May 1921 her father was the first minister for education and leader of the Stormont senate in the newly created parliament of Northern Ireland. He was greatly interested in aviation, and in 1933 gave fifty acres of his estate for the establishment of an aerodrome at Newtownards; he also set up a flying school, in the hope that the facility would become the province's main civilian airport. The family used the aerodrome to travel between London and Mount Stewart; in 1934, Lady Mairi, bringing monkeys for the private zoo at Mount Stewart, was on one of the first flights to land on the grass strip at Newtownards. Lady Mairi learned to fly there, and in February 1934, aged 12, she piloted a plane solo. Newspapers in the United Kingdom and in the USA carried the story and her photograph; her instructor allegedly commented that she was 'as cool as ice'.
The airfield also saw the arrival in 1936 in a large Junkers plane of Joachim von Ribbentrop, the German ambassador to the UK; Lord Londonderry was intent on maintaining good relations with the government of Adolf Hitler, and sought von Ribbentrop's friendship. In pursuance of his unofficial diplomacy, Londonderry took his wife and youngest daughter with him on at least one of his visits to German politicians. Lady Mairi recalled meeting both Hitler and Heinrich Himmler, but neither impressed her; she said Hitler was a nondescript fellow and that Himmler reminded her of a floorwalker in Harrods shop. In later years she defended her father's ill-judged efforts to forge links with Nazi Germany by claiming that he was doing all he could to prevent another war. When the second world war started, Lady Mairi joined the motor transport section of the Women's Legion, founded by her mother in 1915 during the first world war, and drove pickups in the London docks. Her fiancé, the Hon. Derek William Charles Keppel, Viscount Bury, a captain in the 13th/18th Royal Hussars, shared her interest in flying and was seconded to the Royal Air Force (1938–42). The couple married on 10 December 1940, and had two daughters, before divorcing in 1958.
Before and after her divorce, Lady Mairi Bury lived for the most part in Mount Stewart. Her father had had a difficult relationship with his only son, and, much to her brother's chagrin, Lady Mairi and her mother inherited the Mount Stewart estate when the 7th earl died in 1949. Lady Mairi was an enthusiastic gardener, keen to maintain the beautiful gardens created by her mother, Lady Edith. In 1957 the gardens were handed over to the National Trust to ensure their survival and upkeep. Lady Mairi Bury continued to live in an apartment in Mount Stewart, even after she gave the house and most of the contents to the trust in 1976, although she generally avoided contact with the thousands of visitors to the property. Following in her father's footsteps, Lady Bury served as a JP in Co. Down, but when the Good Friday agreement was signed in 1998 she was outraged, and broke with the family tradition of support for the official Ulster Unionist Party. She felt that the interests of Northern Ireland had not been guaranteed, and joined the Democratic Unionist Party in protest.
She was involved in local sports as commodore of Newtownards Sailing Club and life president of Ards Football Club. Lady Bury was also a notable racehorse owner, with the first thoroughbred stud in Northern Ireland. She twice won the Gold Cup at Ascot with her horse Fighting Charlie, and once won the Irish Thousand Guineas with Northern Gleam; she also regularly exhibited colts and yearlings at the Royal Ulster Agricultural Society's show at Balmoral, Belfast. An even more important interest throughout her life, however, was philately. From the age of eight, unusually for a girl, Lady Mairi collected stamps. For the next eighty years, she sought out rarities, and also collected letters and envelopes relating to notorious events and scandals in the nineteenth century. She never put any of her collection into a bank vault or even a safe, so that she could readily work on it at any time, and as an acknowledged and painstaking expert was elected a fellow of the Royal Philatelic Society, London. She owned several of the rarest stamps in the world. The collection was put up for sale after her death; Sotheby's described it as the finest collection to be auctioned in more than twenty-five years, and it was said to be the finest collection ever amassed by a woman. She had collected tens of thousands of stamps, including examples of all penny blacks ever produced; an unissued penny black from April 1840 sold for £36,000, and the collection also boasted a penny black used on 6 May 1840, the first day that postage stamps were officially used. An unused twopenny blue broke previous records at £43,200, but the top-selling lot in the sale was Lady Mairi's unique collection of King Edward VII stamps, mounted on ninety-one pages to the highest exhibition standard. The lot fetched £66,000; the total achieved by all 2,185 lots was £3,045,924.
Lady Mairi Bury died at Mount Stewart on 16 November 2009, and was buried in Tir na nÓg ('Land of Youth'), the family burial ground in the garden at Mount Stewart. Nearby, Mairi's Garden preserves the name and memory of the baby who slept there in her pram, and who, more than seventy years later, was to give her beautiful home to the National Trust for the public to enjoy.