from Wikipedia:

Margaret Peverell, Countess of Derby (b. circa 1114, Nottinghamshire, England), was an English noblewoman who lived at Tutbury Castle in Staffordshire, England.
Family and marriage
Margaret was the daughter of William Peverel the Younger of Peveril Castle in Derbyshire and his wife, Oddona (Sources:Hal Bradley:
1. Cokayne, George Edward, The Complete Peerage of England, Scotland, Ireland, Great Britain and the United Kingdom, Extant, Extinct, or Dormant (London: St. Catherine Press, 1910.), 4:311, Los Angeles Public Library, 929.721 C682.
2. Keats-Rohan, K.S.B., Domesday People: A Prosopography of Persons Occurring in English Documents, 1066-1166 (Woodbridge: The Boydell Press, 1999.), pp. 361, 494, Los Angeles Public Library, Gen 942.02 K25.
3. Sheppard, Walter Lee, F.A.S.G., "Royal Bye-Blows: The Illegitimate Children of the English Kings," NEHGR 119:2 (Apr 1965) (New England Historic, Genealogical Society.), p. 95, Los Angeles Public Library.. Her grandfather was William Peverel.
She married Robert Ferrers and thus became Countess of Derby. She was the mother of William de Ferrers, 3rd Earl of Derby, Walkelin de Ferrers and a daughter, Petronella.[citation needed]
She died in 1154 and was buried in Merevale Abbey.


Margaret Ferrers' effigy in Merevale Abbey