The King died on
20 January 1936, after his physician, the future
Baron Dawson of Penn, gave him an injection of
morphine and
cocaine which may have hastened his death. Queen Mary's eldest son,
Edward, Prince of Wales, ascended the throne as Edward VIII. She was now
Queen Mother (see
English Queen Mothers), though she did not use that title and was instead known as
Her Majesty Queen Mary.
Within the year, the new King caused a
constitutional crisis by announcing his desire to marry his twice-divorced American mistress, Mrs.
Wallis Simpson. Queen Mary disapproved of divorce, which was against the teaching of the
Anglican Church, and thought Mrs. Simpson wholly unsuitable as the wife of a King. After receiving advice from the
Prime Minister of the United Kingdom, Stanley Baldwin, as well as the
Dominion governments, that he could not remain King and marry Mrs. Simpson, Edward
abdicated. Though loyal and supportive of her son, Queen Mary could not comprehend why Edward would neglect his duty as King in favour of his personal feelings. Mrs. Simpson had been presented formally to both King George V and Queen Mary at court, but Queen Mary later refused to meet her either in public or privately. Queen Mary saw it as her duty to provide moral support for her second son, the reserved and stammering
Prince Albert, Duke of York, who ascended the throne in Edward's place as King George VI. She even attended the new King and Queen's coronation, the first
dowager queen ever to do so. Edward’s abdication did not lessen her love for him as her son, but she never wavered in her disapproval of the damage she believed had been done to the Crown.
Queen Mary took an interest in the upbringing of her granddaughters, Princesses Elizabeth and Margaret Rose, taking them on various excursions in London, to art galleries and museums. (The Princesses' own parents thought it unnecessary for them to be taxed with any demanding educational regime.)
During
World War II, George VI wished his mother to be evacuated from London. Although she was reluctant, she decided to live at
Badminton House with her niece,
Mary Somerset, Duchess of Beaufort, the daughter of her brother
Adolphus, Lord Cambridge. Her personal belongings were transported from London in seventy pieces of luggage. Her household, which comprised fifty-five servants, occupied most of the house, except for the Duke and Duchess's private suites, for the next seven years. The only people to complain about the arrangements were the royal servants, who found the house too small, though Queen Mary annoyed her niece by having the ancient ivy torn from the walls, considering it unattractive and a hazard. From Badminton, she supported the war effort by visiting troops and factories, and directing the gathering of scrap materials; she was known to offer lifts to soldiers she spotted on the roads. In 1942, her youngest surviving son,
Prince George, Duke of Kent, was killed in an air crash while on active service. Queen Mary finally returned to
Marlborough House in June 1945, after the war in Europe had resulted in the defeat of
Nazi Germany.
Queen Mary was an eager collector of objects and pictures with a Royal connection. She paid above-market estimates when purchasing jewels from the estate of
Dowager Empress Marie Feodorovna and paid almost three times the estimate when buying the family's Cambridge Emeralds from Lady Kilmorey, mistress of her late brother
Prince Francis. In 1924, the famous architect
Sir Edwin Lutyens created
Queen Mary's Dolls' House for her collection of miniature pieces. Indeed, she has sometimes been criticised for her aggressive acquisition of
objets d'art for the
Royal Collection. On several occasions, she would express to hosts, or others, that she admired something they had in their possession, in the expectation that the owner would be willing to donate it. Her extensive knowledge of, and research into, the Royal Collection helped in identifying artifacts and artwork that had gone astray over the years. The Royal Family had loaned out many objects to British friends over previous generations. Once she had identified unreturned items through old inventories, she would write to the holders to request them back.
In 1952, King George VI died, the third of Queen Mary's children to predecease her, and her eldest granddaughter,
Princess Elizabeth, ascended the throne. Queen Mary died the next year of
lung cancer (referred to publicly as "gastric problems") at the age of 85, only ten weeks before Elizabeth II's
coronation. She let it be known that, in the event of her death, the coronation was not to be postponed. Her remains
lay in state at
Westminster Hall, where large numbers of mourners filed past her coffin. She is buried in the nave of
St. George's Chapel, Windsor, beside her husband.