General Notes

The History of the Commoners, Vol II, page 271, by Burke, states that Richard Chambernon "married the heiress of Sir Alexander Okeston, by his wife, Joan, relict of Richard de Valletort." This Joan has no surname. In a footnote, Burke states that "This Joan, or Jone, is supposed to have been a concubine of Richard Plantagenet, Earl of Cornwall, King of the Romans."  Burke continues in the main entry, "By her, whom Edmond, Earl of Cornwall, calleth by the name of sister, in a grant made by him, dated 12th Edward I. (Richard Chambernon) had a son and heir, Sir Richard Chambernon..." Richard de Cornwall has a daughter Joan, half-sister of Edmond de Cornwall, recorded in some sources as married to Richard Champernowne, so this indicates that Champernowne married a daughter of Richard de Cornwall, not a daughter of Sir Alexander Okeston.

Wadham College, Oxford by: T.G. Jackson  States  Richard de Cornwall, King of the Romans, had as a concubine "Joan, 2nd da. and co-heir of Richard de Valletort, widow of Sir Alex. Oakeston", with a son Richard and a daughter Joan, by her. The daughter is recorded as marrying Richard Champernowne. By this account, Joan the concubine was the daughter of Richard de Valletort, not the widow.

A Genealogical and Heraldic History of the Commoners of Great Britain and Ireland, Enjoying Territorial Possessions or High Official Rank; But Uninvested with Heritable Honours.  By: John Burke, Publication: 1836, Vols. I - IV
Wadham College Oxford, T.G. Jackson, author.  Its Foundation Architecture and History with an Account of the Family of Wadham and Their Seats in Somerset and Devon.
Visitation of the County of Devon, 1620, By: Vivian, John Lambrick, Published By: Henry S. Eland, Exeter, 1895.
Comprising the Heralds' Visitations of 1531, 1564, & 1620. With additions by Lieutenant-Colonel J.L. Vivian.