Saxe-Meiningen was a small state, covering about . It was the most liberal German state and, unlike its neighbours, permitted a free press and criticism of the ruler.
Considerable allowances were likely to be voted by Parliament to any Royal Duke who married, and this acted as a further incentive for William to marry. Adelaide was a princess from an unimportant German state, but William had a limited choice of available princesses and, after deals with other candidates fell through, a marriage to Adelaide was arranged. The allowance proposed was slashed by Parliament, and the outraged Duke considered calling off the marriage. However, Adelaide seemed the ideal candidate: amiable, home-loving, and willing to accept William's illegitimate children as part of the family. The arrangement was settled and William wrote to his eldest son, "She is doomed, poor dear innocent young creature, to be my wife.
Adelaide married William in a double marriage with William's brother, Prince Edward, Duke of Kent and his bride, Victoria, the Dowager Princess of Leiningen on 11 July 1818, at Kew Palace in Surrey, England. They had only met each other for the first time about a week earlier, on [4 July at Grillon's Hotel in Bond Street. Neither William nor Adelaide had been married before, and William was twenty-seven years her senior.
Despite these unromantic circumstances, the couple settled amicably in Hanover (where the cost of living was much lower than in England), and by all accounts were devoted to each other throughout their marriage. Adelaide smartened up William's behaviour; he drank less, swore less and became more tactful. Observers thought them parsimonious, and their lifestyle simple, even boring. William eventually accepted the reduced increase in his allowance voted by Parliament.
On the Continent, Adelaide became pregnant but in her seventh month of pregnancy, she caught pleurisy and during the illness she gave birth prematurely. Her daughter, Charlotte, lived for only a few hours. Another pregnancy in the same year caused William to move the household to England so his future heir would be born on English soil, yet Adelaide miscarried in Calais during the journey (5 September 1819). She became pregnant again, and a second daughter, Elizabeth, was born in December 1820. Elizabeth seemed strong but died aged only four months of "inflammation in the Bowels". Ultimately, William and Adelaide had no surviving children. Twin boys were stillborn on 8 April 1822, and a possible brief pregnancy may have occurred within the same year.
Princess Victoria of Kent came to be acknowledged as William's heir, as Adelaide had no further pregnancies. While there were rumours of pregnancies well into William's reign (dismissed by the King as "damned stuff"), they seem to have been without basis.
Adelaide was beloved by the British people for her piety, modesty, charity, and her tragic childbirth history. A large portion of her household income was given to charitable causes. She also treated the young Princess Victoria of Kent (William's heir presumptive and later Queen Victoria) with kindness, despite her own inability to produce an heir and the open hostility between William and Victoria's mother, the Duchess of Kent. She refused to have women of questionable virtue attend her Court. Wrote Clerk of the Privy Council Charles Greville of her, "The Queen is a prude and refuses to have the ladies come décolletées to her parties. George the 4th, who liked ample expanses of that kind, would not let them be covered.
Adelaide attempted, perhaps unsuccessfully, to influence the King politically. She never spoke about politics in public, however, she was strongly Tory. It is unclear how much of William's attitudes during the passage the Reform Act 1832 were due to her influence. The Press, the public and courtiers assumed that she was agitating behind the scenes against reform, but she was careful to be non-committal in public. As a result of her partiality, she became unpopular with reformers. Unbelievable rumours circulated that she was having an affair with her Lord Chamberlain, the Tory Lord Howe, but almost everyone at court knew that Adelaide was inflexibly pious and was always faithful to her husband. The Whig Prime Minister, Lord Grey, had Lord Howe removed from Adelaide's household. Attempts to reinstate him after the Reform Bill had passed were not successful as Lord Grey and Lord Howe could not come to an agreement as to how independent Howe could be of the government.
In October 1834 a great fire destroyed much of the Palace of Westminster, which Adelaide considered divine retribution for the vagaries of reform. When the Whig ministry of Lord Melbourne was dismissed by the King, The Times newspaper blamed the Queen's influence, though she seems to have had very little to do with it. Influenced by her similarly reactionary brother-in-law, the Duke of Cumberland, she did write to the King against reform of the Church of Ireland.
Both William and Adelaide were fond of their niece, Princess Victoria of Kent, and wanted her to be closer to them. Their efforts were frustrated by Victoria's mother, the Duchess of Kent. The Duchess refused to acknowledge Adelaide's precedence, left letters from Adelaide unanswered and commandeered space in the royal stables and apartments for her own use. The King, aggrieved at what he took to be disrespect from the Duchess to his wife, bluntly announced in the presence of Adelaide, the Duchess, Victoria and many guests, that the Duchess was "incompetent to act with propriety", that he had been "grossly and continually insulted by that person", and that he hoped to have the satisfaction of living beyond Victoria's age of majority, so that the Duchess of Kent would never be Regent. Everyone was aghast at the vehemence of the speech, and all three ladies were deeply upset. The breach between the Duchess and the King and Queen was never fully healed, but Victoria always viewed both of them with kindness.
Queen Victoria, who never forgot her aunt Adelaide's kindness to her, remembered her at the christening of her firstborn child, Victoria Adelaide Mary Louise.
| Name | Birth | Death | Notes |
|---|---|---|---|
| Princess Charlotte of Clarence | 21 March 1819 | 21 March 1819 | |
| Princess Elizabeth of Clarence | 10 December 1820 | 4 March 1821 | |