What claim did Richard III use to argue that Edward IV’s children were illegitimate?

To justify his usurpation of the throne, Richard III claimed that the children of Edward IV were illegitimate and therefore disqualified from the crown.1

His argument relied on the so-called "precontract" story, which alleged that Edward IV had previously betrothed himself to Lady Eleanor Butler. At the time, such a betrothal was considered as binding as a marriage, meaning Edward IV was not free to marry his queen, Elizabeth Wydeville. Consequently, Richard III asserted that any children born to Elizabeth were illegitimate.12

Historians note that there is no contemporary evidence to support this claim of a precontract, and it was never adjudicated by a competent church court. Many scholars believe the argument was likely a pretext invented to justify a usurpation that Richard had already decided to carry out.1