Catherine Sedley, Countess of Dorchester

Catherine was the only legitimate child of the Restoration poet Sir Charles Sedley. Her mother was Lady Catherine Savage, daughter of John Savage, 2nd Earl Rivers. She grew up "notoriously plain" (being brunette and thin rather than plump and fair). While her father roistered around England, her mother spiralled into insanity until she entered a psychiatric hospital in Ghent in Catherine's early teens. At this low point in her life, Sir Charles introduced a common-law wife, Anne Ayscough, into the family and ejected Catherine from the house.[4]

Catherine Sedley circa 1685

She worked for the Italian princess Mary of Modena, who had just married James, Duke of York, heir to the British throne. This eventually led to an affair with him.[1] She was bewildered at having been chosen by James. "It cannot be my beauty for he must see I have none," she remarked incredulously. "And it cannot be my wit, for he has not enough to know that I have any."[5] James in fact was often attracted to women like Catherine and Arabella Churchill who were generally considered plain, if not ugly; his brother Charles II once joked that his confessor must impose these mistresses on him as a penance.

After his accession James yielded to pressure from his confessor Fr. Bonaventure Giffard, backed by the Earl of Sunderland and several Catholic councillors, and put her away for a time.[1] While James by his own account took Giffard's intervention "very kindly, he being a truly religious man" he told his councillors sharply "not to meddle in things that in no way related to them," adding, with a rare touch of humour, that he had not realised that they had all entered the priesthood too.

She was created Countess of Dorchester for life in 1686, an elevation which aroused much indignation and compelled Catherine to reside for a time in Ireland. In 1696 she married Sir David Colyear, Bt.,[6] who was created Earl of Portmore in 1703, and she was thus the mother of Charles Colyear, 2nd Earl of Portmore. After the Glorious Revolution when Queen Mary II refused to receive her at Court, Catherine inquired how Mary, who had broken the commandment to honour her father, was in any way better than Catherine, who had broken the commandment against adultery.

At the court of George I she met Charles II's mistress Louise de Kérouaille, Duchess of Portsmouth, and William III's mistress Elizabeth Hamilton, Countess of Orkney, and exclaimed "God! Who would have thought that we three whores should meet here."[7] At George's coronation in 1714 when the Archbishop of Canterbury, Thomas Tenison, ritually asked if the people accepted their new King, Catherine, observing the number of soldiers on duty, asked caustically "Does the old fool think that anyone will say No?"

She died at Bath on 26 October 1717,[8] aged 59, when her life peerage became extinct.

By James II, Lady Dorchester had a daughter, Lady Catherine Darnley, (died 1743), who married James Annesley, 3rd Earl of Anglesey, and after his death married John Sheffield, 1st Duke of Buckingham and Normanby. Through Catherine Darnley she was the ancestress of the Barons Mulgrave and of the Mitford sisters. Through her son, Charles, Lord Portmore, she was the grandmother of Elizabeth Collier, wife of Dr Erasmus Darwin, the physician, scientist, poet and grandfather of Charles Darwin.

• English royal mistress

•  This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Sedley, Sir Charles". Encyclopædia Britannica (11th ed.). Cambridge University Press.

• Seccombe, Thomas (1897). "Sedley, Catherine" . Dictionary of National Biography. 51.