Elizabeth was the daughter of Sir Robert Killigrew, a royalist courtier and politician who served under both James I and Charles I. In 1639 she married Francis Boyle, the son of Richard Boyle, 1st Earl of Cork and an Irish landowner.

The young Elizabeth and her husband joined the royalist court-in-exile in France sometime in the mid-to-late 1640’s, where she became a maid of honour to Queen Henrietta-Maria, the mother of Charles II. Elizabeth probably first met Charles around October 1651 when he returned to Paris after his failed rebellion in England, and some time that year they began an affair. In 1652 she gave birth to his daughter, Charlotte.

Elizabeth and her husband returned to England around 1660 upon the Restoration, when Francis was granted the Irish peerage of Viscount Shannon, making Elizabeth a Viscountess. This may have been for their loyalty to Charles during his years in exile, but as Charles had a track record of rewarding his mistresses for their unique ‘services’, it could have been that the peerage was more for Elizabeth than Francis.

Little else is known about Elizabeth, her relationship with Charles, or their daughter, as the evidence about them is thin. However, at some point (probably after the Restoration) Charles recognised Charlotte as his child, and she was given the surname FitzRoy: ‘son of king’, like some of her other illegitimate half-brothers and sisters.

There are no known portraits of Elizabeth, or her daughter Charlotte, which is a shame, but it does suggest that Elizabeth was more discreet than the other women in Charles II’s life.