Estrildis was the beloved mistress of King Locrinus of the Britons and the mother of his daughter Habren, according to the 12th-century chronicler Geoffrey of Monmouth.
[4] Locrinus was forced to honour his prior betrothal to Gwendolen, the daughter of King Corineus of Cornwall, but kept Estrildis as his mistress.
Elstridis and her story feature in Elstrild by Charles Tilney (d. 1586),[8] The Faerie Queene (1590) by Edmund Spenser, The Complaynt of Elstred (1593) by Thomas Lodge, and Locrine (1887) by Swinburne.
[2] A variant of the story is told by Oliver Mathews, in which Estrildis is called Sŵs-wên, and Locrinus builds Caersws for her.
[9][10][11] The story went on to inspire the folktale of Rosamund Clifford, mistress of King Henry II, being hidden in an underground labyrinth.