Sophia von Kielmansegg, Countess of Leinster and Darlington

Sophia Charlotte von Kielmansegg, Countess of Darlington and Countess of Leinster (1675 – 20 April 1725) was a German-born British courtier and a half-sister of George I of Great Britain.

Born Baroness Sophia Charlotte von Platen und Hallermund (probably in Osnabrück), she was the daughter of Clara Elisabeth von Meysenburg, Baroness von Platen und Hallermund (1648–1700) and Ernest Augustus, Elector of Hanover. Her mother's husband, Franz Ernst, Baron von Platen (1631–1709) was officially described as her father (as indeed he was in that, at the time, the child of a married woman was conclusively presumed to be the child of her husband) but the fact that she was the illegitimate daughter of the Elector was acknowledged at court. When her "father" was accorded a comital title in 1689, she became Countess Sophia.

Sophia established a close relationship with her half-brother George Louis, who succeeded to the British throne as George I in 1714, but his mother, Electress Sophia, asserted that, 'to her certain knowledge', Countess Sophia was not one of George's mistresses. In 1701, she married Johann Adolf, Baron von Kielmansegg (1668–1717), Deputy Master of the Horse to George Louis and they had three sons and two daughters, the eldest of whom, Charlotte (1703–1782), married Emanuel Howe, 2nd Viscount Howe.

When George Louis became King of Great Britain on the death of Queen Anne in 1714, Sophia and her family followed him to London. She mixed well with the king's British courtiers (who also assumed her to be one of the king's mistresses) but competed for influence with George's mistress, Melusine von der Schulenburg, and was disliked by the Princess of Wales, who 'thought her a wicked woman'. Sophia received many gifts from those seeking patronage; e.g. between 1715 and 1720 she received £9,545 from the Duke of Chandos and in 1720 was given £15,000 of stock by the South Sea Company, with a bonus of £120 for every point the stock rose above £154.

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