Page "History of England" Paragraph 72

A more serious menace was Perkin Warbeck, a Flemish youth who posed as Edward IV's son Richard.

Again enjoying the support of Margaret of Burgundy, he invaded England four times from 1495-1497 before he was finally captured and put in the Tower of London.

Both Warbeck and the Earl of Warwick were too dangerous to keep around even in captivity, and Henry had to execute them in 1499 before Ferdinand and Isabella of Spain would allow their daughter Catherine to come to England and marry his son Arthur.