A Welsh courtier with the boldness to bed the queen lost his head this date in 1461 … but his career in usurpation was just getting started. The House of Tudor that would come to rule England counted Owen its sire; the four-year-old grandson he left at his death grew up to become the first Tudor monarch, Henry VII. Owen produced the root of this august line with Dowager Queen Catherine of Valois, the French princess Henry V had extracted as part of the price of peace after Agincourt. That union was supposed to join the two great realms, but...